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Aims: Risk factors for asymptomatic echocardiographic abnormalities that predict symptomatic heart failure (HF) may provide insight into early mechanisms of HF pathogenesis. We examined risk factors associated with asymptomatic echocardiographic structural, systolic, and diastolic abnormalities, separately and in combination, and interactions between risk factors, in the prospective community-based SCReening Evaluation of the Evolution of New HF (SCREEN-HF) Study cohort of 3190 participants at increased risk of cardiovascular disease., Methods and Results: Inclusion criteria were age ≥ 60 years with one or more of hypertension, diabetes, ischaemic heart disease, valvular heart disease, abnormal heart rhythm, cerebrovascular disease, or renal impairment. Exclusion criteria were known HF, ejection fraction < 50%, or >mild valve abnormality. Structural, systolic, and diastolic echocardiographic abnormalities were defined according to the Atherosclerosis Risk in Communities study criteria, and risk factors for asymptomatic structural, systolic, and diastolic abnormalities were identified using logistic regression analysis. In multivariable analysis, increased body mass index (BMI), non-steroidal anti-inflammatory drug therapy, and alcohol intake were risk factors for isolated structural abnormality, whereas male gender, increased heart rate, atrial fibrillation (AF), angiotensin-converting enzyme inhibitor therapy, and obstructive sleep apnoea were associated with a lower risk. Moreover, male gender, smoking, increased systolic blood pressure, and physical inactivity were risk factors for isolated systolic abnormality, whereas increased pulse pressure and antihypertensive therapy were associated with a lower risk. Furthermore, increased age, blood pressure, amino-terminal pro-B-type natriuretic peptide level, and warfarin therapy (associated with AF) were risk factors for isolated diastolic abnormality, whereas increased heart rate and triglyceride level (associated with BMI) were associated with a lower risk. The association of increased heart rate with lower risk of structural and diastolic abnormalities was independent of β-blocker therapy. Interactions between risk factors differed for structural, systolic, and diastolic abnormalities., Conclusions: The different risk factors for asymptomatic structural, systolic, and diastolic abnormalities that predict symptomatic HF, and the interactions between risk factors, illustrate how these structural, systolic, and diastolic abnormalities represent unique trajectories that lead to symptomatic HF. Improved understanding of these trajectories may assist in the design of HF prevention strategies., (© 2021 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.)

Background: Given the age-related decline in glomerular filtration rate (GFR) in healthy individuals, we examined the association of all-cause death or cardiovascular event with the Kidney age - Chronological age Difference (KCD) score, whereby an individual's kidney age is estimated from their estimated GFR (eGFR) and the age-dependent eGFR decline reported for healthy living potential kidney donors., Methods: We examined the association between death or cardiovascular event and KCD score, age-dependent stepped eGFR criteria (eGFRstep), and eGFR < 60 ml/min/1.73 m 2 (eGFR60) in a community-based high cardiovascular risk cohort of 3837 individuals aged ≥60 (median 70, interquartile range 65, 75) years, followed for a median of 5.6 years., Results: In proportional hazards analysis, KCD score ≥ 20 years (KCD20) was associated with increased risk of death or cardiovascular event in unadjusted analysis and after adjustment for age, sex and cardiovascular risk factors. Addition of KCD20, eGFRstep or eGFR60 to a cardiovascular risk factor model did not improve area under the curve for identification of individuals who experienced death or cardiovascular event in receiver operating characteristic curve analysis. However, addition of KCD20 or eGFR60, but not eGFRstep, to a cardiovascular risk factor model improved net reclassification and integrated discrimination. KCD20 identified individuals who experienced death or cardiovascular event with greater sensitivity than eGFRstep for all participants, and with greater sensitivity than eGFR60 for participants aged 60-69 years, with similar sensitivities for men and women., Conclusions: In this high cardiovascular risk cohort aged ≥60 years, the KCD score provided an age-adapted measure of kidney function that may assist patient education, and KCD20 provided an age-adapted criterion of eGFR-related increased risk of death or cardiovascular event. Further studies that include the full age spectrum are required to examine the optimal KCD score cut point that identifies increased risk of death or cardiovascular event, and kidney events, associated with impaired kidney function, and whether the optimal KCD score cut point is similar for men and women., Trial Registration: ClinicalTrials.gov NCT00400257 , NCT00604006 , and NCT01581827 .

Aim: Heart failure (HF) incidence increases markedly with age. We examined age-associated longitudinal change in cardiac structure and function, and their prediction by age and cardiovascular disease (CVD) risk factors, in a community-based cohort aged ≥60 years at increased CVD risk but without HF., Methods and Results: CVD risk factors were recorded in 3065 participants who underwent a baseline echocardiographic examination, of whom 2358 attended a follow-up examination 3.8 [median, inter-quartile range (IQR) 3.5, 4.2] years later. Median age was 71 (IQR 67, 76) years and 55% of participants were male. Age was associated with longitudinal increase in left ventricular (LV) mass index (LVMI); decrease in LV volumes; increase in LV ejection fraction; decrease in mitral annular systolic velocity; decrease in diastolic function (decreased mitral early diastolic annular velocity (e'); and increase in left atrial volume index, mitral peak early diastolic flow velocity (E)/e' ratio, and tricuspid regurgitant velocity (TR Vmax ) in men and women, except for TR Vmax in men). In multivariable analysis, longitudinal increase in LVMI was explained by CVD risk factors alone, whereas age, together with CVD risk factors, independently predicted longitudinal change in all other echocardiographic parameters. CVD risk factors were differentially associated with longitudinal change in different echocardiographic parameters., Conclusions: Whereas the increase in LVMI with age was explained by CVD risk factors alone, age, together with risk factors, independently predicted longitudinal change in all other echocardiographic parameters, providing evidence for age-specific mechanisms of change in cardiac structure and function as people age. Age-associated change in LVMI, LV volumes, and diastolic function resembled what might be expected for the evolution of HF with preserved ejection fraction. Given the differential association of different CVD risk factors with longitudinal change in different echocardiographic parameters, therapies aimed at attenuation of age-associated change in cardiac structure and function, and HF evolution, will likely need to address multiple CVD risk factors., (© 2020 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.)

Background: Body mass index † Deceased. (BMI) is a risk factor for heart failure with preserved ejection fraction (HFpEF)., Design: We investigated the threshold BMI and sex-specific waist circumference associated with increased HFpEF incidence in the SCReening Evaluation of the Evolution of New Heart Failure (SCREEN-HF) study, a cohort study of a community-based population at increased cardiovascular disease risk., Methods: Inclusion criteria were age ≥60 years with one or more of self-reported hypertension, diabetes, heart disease, abnormal heart rhythm, cerebrovascular disease or renal impairment. Exclusion criteria were known heart failure, ejection fraction <50% or more than mild valve abnormality. Among 3847 SCREEN-HF participants, 73 were diagnosed with HFpEF at a median of 4.5 (interquartile range: 2.9-5.5) years after enrolment., Results: HFpEF incidence rates were higher for BMI ≥27.5 kg/m 2 than for BMI < 25 kg/m 2 , and for waist circumference >100 cm (men) or > 90 cm (women) than for waist circumference ≤94 cm (men) or ≤ 83 cm (women) in Poisson regression analysis. Semiparametric proportional hazards analyses confirmed these BMI and waist circumference thresholds, and exceeding these thresholds was associated with an attributable risk of HFpEF of 44-49%., Conclusions: Both central obesity and overweight were associated with increased HFpEF incidence. Although a randomised trial of weight control would be necessary to establish a causal relationship between obesity/overweight and HFpEF incidence, these data suggest that maintenance of BMI and waist circumference below these thresholds in a community similar to that of the SCREEN-HF cohort may reduce the HFpEF incidence rate by as much as 50%.

tRNAs are short noncoding RNAs required for protein translation. The human genome includes more than 600 putative tRNA genes, many of which are considered redundant. tRNA transcripts are subject to tightly controlled, multistep maturation processes that lead to the removal of flanking sequences and the addition of nontemplated nucleotides. Furthermore, tRNAs are highly structured and posttranscriptionally modified. Together, these unique features have impeded the adoption of modern genomics and transcriptomics technologies for tRNA studies. Nevertheless, it has become apparent from human neurogenetic research that many tRNA biogenesis proteins cause brain abnormalities and other neurological disorders when mutated. The cerebral cortex, cerebellum, and peripheral nervous system show defects, impairment, and degeneration upon tRNA misregulation, suggesting that they are particularly sensitive to changes in tRNA expression or function. An integrated approach to identify tRNA species and contextually characterize tRNA function will be imperative to drive future tool development and novel therapeutic design for tRNA-associated disorders.

Aims: We investigated whether addition of diastolic dysfunction (DD) and longitudinal strain (LS) to Stage B heart failure (SBHF) criteria (structural or systolic abnormality) improves prediction of symptomatic HF in participants of the SCReening Evaluation of the Evolution of New Heart Failure study, a self-selected population at increased cardiovascular disease risk recruited from members of a health insurance fund in Melbourne and Shepparton, Australia. Both American Society of Echocardiography and European Association of Cardiovascular Imaging (ASE/EACVI) criteria and age-specific Atherosclerosis Risk in Communities (ARIC) study criteria, for SBHF and DD, and ARIC criteria for abnormal LS, were examined., Methods and Results: Inclusion criteria were age ≥60 years with one or more of self-reported ischaemic or other heart disease, irregular or rapid heart rhythm, cerebrovascular disease, renal impairment, or treatment for hypertension or diabetes for ≥2 years. Exclusion criteria were known HF, or ejection fraction <50% or >mild valve abnormality detected on previous echocardiography or other imaging. Echocardiography was performed in 3190 participants who were followed for a median of 3.9 (interquartile range: 3.4, 4.5) years after echocardiography. Symptomatic HF was diagnosed in 139 participants at a median of 3.1 (interquartile range: 2.1, 3.9) years after echocardiography. ARIC structural, systolic, and diastolic abnormalities predicted HF in univariate and multivariable proportional hazards analyses, whereas ASE/EACVI structural and systolic, but not diastolic, abnormalities predicted HF. ARIC and ASE/EACVI SBHF criteria predicted HF with sensitivities of 81% and 55%, specificities of 39% and 76%, and C statistics of 0.60 (95% confidence interval: 0.57, 0.64) and 0.66 (0.61, 0.71), respectively. Adding ARIC DD to SBHF increased sensitivity to 94% with specificity of 24% and C statistic of 0.59 (0.57, 0.61), whereas addition of ASE/EACVI DD to SBHF increased sensitivity to 97% but reduced specificity to 9% and the C statistic to 0.52 (0.50, 0.54, P < 0.0001). Addition of LS to ARIC or ASE/EACVI SBHF criteria had minimal impact on prediction of HF., Conclusions: Age-specific ARIC DD criteria, but not ASE/EACVI DD criteria, predicted symptomatic HF, and addition of age-specific ARIC DD criteria to ARIC SBHF criteria improved prediction of symptomatic HF in asymptomatic individuals with cardiovascular disease risk factors. Addition of LS to ASE/EACVI or ARIC SBHF criteria did not improve prediction of symptomatic HF., (© 2019 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of the European Society of Cardiology.)

Aims: We investigated which serum amino-terminal pro-B-type-natriuretic peptide (NT-proBNP) levels inform heart failure (HF) risk in a community-based population at increased cardiovascular disease (CVD) risk., Methods and Results: Inclusion criteria were age ≥ 60 years with one or more of self-reported hypertension, diabetes, heart disease, abnormal heart rhythm, cerebrovascular disease, or renal impairment. Exclusion criteria were known HF, ejection fraction (EF) < 50%, or more than mild valve abnormality. NT-proBNP levels were measured in 3842 participants on enrolment. HF was diagnosed in 162 participants at a median of 4.5 (interquartile range 2.7-5.4) years after enrolment, 73 with HF with preserved EF (HFpEF), 53 with HF with reduced EF (HFrEF), and 36 with valvular HF (VHF). Areas under the receiver operating characteristic curve (AUC) for 5-year prediction of total HF were similar for NT-proBNP alone (0.79, 95% confidence interval 0.74-0.83) and a 7-parameter multivariable model (0.82, 0.77-0.86, P = 0.035). NT-proBNP cut-points of 11, 16, and 25 pmol/L for individuals aged 60-69, 70-79, and ≥ 80 years, respectively, achieved sensitivities > 76% and specificities of 47-69% for 5-year prediction of total HF in men and women in all three age groups. Sensitivities were ≥ 75% in most subgroups according to body mass index, estimated glomerular filtration rate, and the presence or absence of atrial fibrillation, pacemaker, or CVD, and for the prediction of HFpEF, HFrEF and VHF., Conclusion: Age-specific serum NT-proBNP levels inform prognosis, and hence therapeutic decisions, regarding HF risk in individuals at increased CVD risk., (© 2019 The Authors. European Journal of Heart Failure © 2019 European Society of Cardiology.)

Background: The lack of effective therapies for heart failure with preserved ejection fraction (HFpEF) reflects an incomplete understanding of its pathogenesis., Design: We analysed baseline risk factors for incident HFpEF, heart failure with reduced ejection fraction (HFrEF) and valvular heart failure (VHF) in a community-based cohort., Methods: We recruited 2101 men and 1746 women ≥60 years of age with hypertension, diabetes, ischaemic heart disease (IHD), abnormal heart rhythm, cerebrovascular disease or renal impairment. Exclusion criteria were known heart failure, left ventricular ejection fraction <50% or valve abnormality >mild in severity. Median follow-up was 5.6 (IQR 4.6-6.3) years., Results: Median time to heart failure diagnosis in 162 participants was 4.5 (IQR 2.7-5.4) years, 73 with HFpEF, 53 with HFrEF and 36 with VHF. Baseline age and amino-terminal pro-B-type natriuretic peptide levels were associated with HFpEF, HFrEF and VHF. Pulse pressure, IHD, waist circumference, obstructive sleep apnoea and pacemaker were associated with HFpEF and HFrEF; atrial fibrillation (AF) and warfarin therapy were associated with HFpEF and VHF and peripheral vascular disease and low platelet count were associated with HFrEF and VHF. Additional risk factors for HFpEF were body mass index (BMI), hypertension, diabetes, renal dysfunction, low haemoglobin, white cell count and β-blocker, statin, loop diuretic, non-steroidal anti-inflammatory and clopidogrel therapies, for HFrEF were male gender and cigarette smoking and for VHF were low diastolic blood pressure and alcohol intake. BMI, diabetes, low haemoglobin, white cell count and warfarin therapy were more strongly associated with HFpEF than HFrEF, whereas male gender and low platelet count were more strongly associated with HFrEF than HFpEF., Conclusions: Our data suggest a major role for BMI, hypertension, diabetes, renal dysfunction, and inflammation in HFpEF pathogenesis; strategies directed to prevention of these risk factors may prevent a sizeable proportion of HFpEF in the community., Trial Registration Number: NCT00400257, NCT00604006 and NCT01581827., Competing Interests: Competing interests: DJC has received payments from the Australasian Renin Academy for lectures. JMCa has received payments from Pfizer, Servier, Bayer and Alphpharm for lectures. DLP has received payment from Servier for sitting on their advisory board, and from Boehringer Ingelheim, CSL, Merck Sharp & Dohme and Sanofi Aventis for lectures. UB was an employee of Bupa Australia. DL has received honoraria from Pfizer, Sanofi, Astra-Zeneca, Abbott, Bayer, MSD, GSK, Novartis and Nycomed. SS has received unrestricted educational grants from Schering Plough and Boehringer Ingelheim, and was Principal Investigator of the Novartis sponsored Valsartan Intensified Primary Care Reduction of Blood Pressure (VIPER-BP) Study. HK received support from Novartis, Bristol-Myers Squibb and Ardian/Medtronic.

Background: Effective management of cardiovascular and chronic kidney disease risk factors offers longer, healthier lives and savings in healthcare., Aim: To examine risk factor management in participants of the SCReening Evaluation of the Evolution of New Heart Failure study, a self-selected population at increased cardiovascular disease risk recruited from members of a health insurance fund in Melbourne and Shepparton, Australia., Methods: Inclusion criteria were age ≥ 60 years with one or more self-reported ischaemic or other heart diseases, irregular or rapid heart rhythm, cerebrovascular disease, renal impairment or treatment for hypertension or diabetes for ≥2 years. Exclusion criteria were known heart failure or cardiac abnormality on echocardiography or other imaging. Medical history, clinical examination, full blood examination and biochemistry (without lipids and glycated haemoglobin (HbA1c)) were performed for 3847 participants on enrolment, and blood pressure, lipids and HbA1c were measured 1-2 years after enrolment for 3203 participants., Results: Despite 99% of 3294 participants with hypertension receiving antihypertensive medication, half had blood pressures >140/90 mmHg. Approximately 77% of participants were overweight or obese, with one third being obese. Additionally, 74% of participants at high cardiovascular disease risk had low-density lipoprotein cholesterol levels ≥2 mmol/L, one third of diabetic participants had HbA1c >7%, 22% had an estimated glomerular filtration rate < 60 mL/min/1.73m 2 , and substantial proportions had under-utilisation of antiplatelet therapy and anticoagulation for atrial fibrillation and were physically inactive., Conclusions: This population demonstrated substantial potential to reduce cardiovascular and renal morbidity and mortality and healthcare costs through more effective management of modifiable risk factors., (© 2017 Royal Australasian College of Physicians.)

Background: There is debate whether the J-curve relationship between cardiac event risk and DBP is because of inherent cardiac risk or is a consequence of blood pressure (BP) lowering therapy., Methods: We examined the association between the cardiovascular risk marker amino-terminal-pro-B-type natriuretic peptide (NT-proBNP) and DBP in 1781 women and 2211 men aged at least 60 years with one or more cardiovascular risk factors; exclusion criteria were known heart failure or cardiac abnormality on a cardiac imaging study., Results: The lowest median serum NT-proBNP levels were for DBP 85-89 mmHg for both women and men. DBP less than 70 mmHg in women and less than 80 mmHg in men was associated with higher NT-proBNP levels than the levels at DBP 85-89 mmHg, and this relationship was present for those with SBP equal to or less than 140 and SBP greater than 140 mmHg. In conditional logistic regression models, the association of elevated NT-proBNP levels with low DBP in women was no longer statistically significant after adjustment for age, ischaemic heart disease (IHD), pulse rate, atrial fibrillation, haemoglobin and glomerular filtration rate, whereas the association in men was no longer statistically significant after adjustment for age and IHD. By contrast, the association between elevated NT-proBNP levels and low DBP remained statistically significant after adjustment for the number of antihypertensive drug classes alone or together with all antihypertensive drugs, including β-blocker therapy., Conclusion: There was a J-curve relationship between the cardiovascular risk marker NT-proBNP and DBP that was explained by the clinical variables and not by the BP-lowering therapy.

Increasing evidence for a latent, preclinical phase of cardiac pathology prior to the development of symptomatic heart failure has fuelled interest in the potential of developing a screening program for early disease detection and intervention. Cardiac biomarkers have shown promise in identifying subjects with significant left ventricular dysfunction and more recently to assist in cardiovascular risk stratification. However, a number of questions remain regarding the use of these biomarkers for screening purposes. In particular, appropriate cut-off levels and adjustment for individual patient characteristics still need to be established and further cost-effectiveness studies are required before screening programs can be undertaken. Given the enormous and increasing burden of cardiac failure worldwide, the potential of these biomarkers to identify those at greatest risk of the condition, either alone or as part of a hybrid screening strategy is of great interest to the cardiology community. The aim of this review is to outline evidence behind the argument for screening, discuss the remaining barriers to its development and implementation and highlight potential areas for future research., (Copyright © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). All rights reserved.)

Background: A significant proportion of individuals taking antihypertensive therapies fail to achieve blood pressures <140/90 mmHg. In order to develop strategies for improved treatment of blood pressure, we examined the association of blood pressure control with antihypertensive therapies and clinical and lifestyle factors in a cohort of adults at increased cardiovascular risk., Methods: A cross-sectional study of 3994 adults from Melbourne and Shepparton, Australia enrolled in the SCReening Evaluation of the Evolution of New Heart Failure (SCREEN-HF) study. Inclusion criteria were age ≥60 years with one or more of self-reported ischaemic or other heart disease, atrial fibrillation, cerebrovascular disease, renal impairment or treatment for hypertension or diabetes for ≥2 years. Exclusion criteria were known heart failure or cardiac abnormality on echocardiography or other imaging. The main outcome measures were the proportion of participants receiving antihypertensive therapy with blood pressures ≥140/90 mmHg and the association of blood pressure control with antihypertensive therapies and clinical and lifestyle factors., Results: Of 3623 participants (1975 men and 1648 women) receiving antihypertensive therapy, 1867 (52%) had blood pressures ≥140/90 mmHg. Of these 1867 participants, 1483 (79%) were receiving only one or two antihypertensive drug classes. Blood pressures ≥140/90 mmHg were associated with increased age, male sex, waist circumference and log amino-terminal-pro-B-type natriuretic peptide levels., Conclusions: Most individuals with treated blood pressures above target receive only one or two antihypertensive drug classes. Prescribing additional antihypertensive drug classes and lifestyle modification may improve blood pressure control in this population of individuals at increased cardiovascular risk., (© 2012 The Authors; Internal Medicine Journal © 2012 Royal Australasian College of Physicians.)

The phosphorylated ribosomal protein S6 (pS6) is associated with the 40S ribosomal subunit in eukaryotes and is thought to have a role in RNA storage, degradation, and re-entry into translation. In this study, we found pS6 localized to granulovacuolar degeneration (GVD) within the pyramidal neurons. Immunohistochemical analysis found that nearly 20-fold more neurons contain pS6-positive granules in Alzheimer's disease (AD) hippocampus compared with age-matched controls. Further, pS6-positive granules were more common in neurons not containing neurofibrillary tangles (NFTs), were never associated with extracellular NFTs or in apoptotic neurons, and contained less RNA than neighboring pyramidal neurons not containing pS6-positive granules. In model systems, pS6 is a specific marker for stress granules, and another stress granule protein, p54/Rck, was also found to be a component of GVD in the current study. Stress granules are transient, intracellular, dense aggregations of proteins and RNAs that accumulate as a stress response, protecting cells from apoptosis and inappropriate transcriptional activity, often described as a form of 'molecular triage.' The RNA oxidation modification 8-hydroxyguanosine (8OHG) is strikingly increased in AD, yet this study reports that those neurons with pS6 granules display reduced RNA oxidation demonstrated by lower levels of 8OHG. Since chronic oxidative stress is central to AD pathogenesis, and RNA is a specific oxidative stress target and is intimately associated with stress granule biogenesis in model systems, we suggest that GVD in human brain parallel stress granules, and may in fact be more representative of early disease pathogenesis than traditionally believed. This proposed origin for GVD as a neuroprotective response, may represent a morphologic checkpoint between cell death and reversible cellular stress that proceeds in the absence of other inclusions.

Local control of mRNA translation modulates neuronal development, synaptic plasticity, and memory formation. A poorly understood aspect of this control is the role and composition of ribonucleoprotein (RNP) particles that mediate transport and translation of neuronal RNAs. Here, we show that staufen- and FMRP-containing RNPs in Drosophila neurons contain proteins also present in somatic "P bodies," including the RNA-degradative enzymes Dcp1p and Xrn1p/Pacman and crucial components of miRNA (argonaute), NMD (Upf1p), and general translational repression (Dhh1p/Me31B) pathways. Drosophila Me31B is shown to participate (1) with an FMRP-associated, P body protein (Scd6p/trailer hitch) in FMRP-driven, argonaute-dependent translational repression in developing eye imaginal discs; (2) in dendritic elaboration of larval sensory neurons; and (3) in bantam miRNA-mediated translational repression in wing imaginal discs. These results argue for a conserved mechanism of translational control critical to neuronal function and open up new experimental avenues for understanding the regulation of mRNA function within neurons.

A major pathway of mRNA turnover in eukaryotic cells initiates with deadenylation, leading to mRNA decapping and subsequent 5' to 3' exonuclease digestion. We show that a highly conserved member of the DEAD box family of helicases, Dhh1p, stimulates mRNA decapping in yeast. In dhh1delta mutants, mRNAs accumulate as deadenylated, capped species. Dhh1p's effects on decapping only occur on normal messages as nonsense-mediated decay still occurs in dhh1delta mutants. The role of Dhh1p in decapping appears to be direct, as Dhh1p physically interacts with several proteins involved in mRNA decapping including the decapping enzyme Dcp1p, as well as Lsm1p and Pat1p/Mrt1p, which function to enhance the decapping rate. Additional observations suggest Dhh1p functions to coordinate distinct steps in mRNA function and decay. Dhh1p also associates with Pop2p, a subunit of the mRNA deadenylase. In addition, genetic phenotypes suggest that Dhh1p also has a second biological function. Interestingly, Dhh1p homologs in others species function in maternal mRNA storage. This provides a novel link between the mechanisms of decapping and maternal mRNA translational repression.

Translational stimulation of mRNAs during early development is often accompanied by increases in poly(A) tail length. Poly(A)-binding protein (PAB) is an evolutionarily conserved protein that binds to the poly(A) tails of eukaryotic mRNAs. We examined PAB's role in living cells, using both Xenopus laevis oocytes and Saccharomyces cerevisiae, by tethering it to the 3'-untranslated region of reporter mRNAs. Tethered PAB stimulates translation in vivo. Neither a poly(A) tail nor PAB's poly(A)-binding activity is required. Multiple domains of PAB act redundantly in oocytes to stimulate translation: the interaction of RNA recognition motifs (RRMs) 1 and 2 with eukaryotic initiation factor-4G correlates with translational stimulation. Interaction with Paip-1 is insufficient for stimulation. RRMs 3 and 4 also stimulate, but bind neither factor. The regions of tethered PAB required in yeast to stimulate translation and stabilize mRNAs differ, implying that the two functions are distinct. Our results establish that oocytes contain the machinery necessary to support PAB-mediated translation and suggest that PAB may be an important participant in translational regulation during early development.

Translation and mRNA stability are enhanced by the presence of a poly(A) tail. In vivo, the tail interacts with a conserved polypeptide, poly(A) binding protein (Pab1p). To examine Pab1p function in vivo, we have tethered Pab1p to the 3' UTR of reporter mRNAs by fusing it to MS2 coat protein and placing MS2 binding sites in the 3' UTR of the reporter. This strategy allows us to uncouple Pab1p function from its RNA binding activity. We show that mRNAs that lack a poly(A) tail in vivo are stabilized by Pab1p, and that the portions of Pab1p required for stabilization are genetically distinct from those required for poly(A) binding. In addition, stabilization by Pab1p requires ongoing translation of the mRNA. We conclude that the primary, or sole, function of poly(A) with respect to mRNA stability is simply to bring Pab1p to the mRNA, and that mRNA stabilization is an intrinsic property of Pab1p. The approach we describe may be useful in identifying and assaying 3' UTR regulatory proteins, as it uncouples analysis of function from RNA binding.