14 results on '"Ng, Kah Ying"'
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2. Nonstop mRNAs generate a ground state of mitochondrial gene expression noise
- Author
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Ng, Kah Ying, primary, Lutfullahoglu Bal, Guleycan, additional, Richter, Uwe, additional, Safronov, Omid, additional, Paulin, Lars, additional, Dunn, Cory D., additional, Paavilainen, Ville O., additional, Richer, Julie, additional, Newman, William G., additional, Taylor, Robert W., additional, and Battersby, Brendan J., additional
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- 2022
- Full Text
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3. HIV-1 Transmission Networks Among Men Who Have Sex With Men in Asia
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Ng, Kim Tien, Ng, Kah Ying, Chen, Jonathan Hon-Kwan, Ng, Oon Tek, Kamarulzaman, Adeeba, and Tee, Kok Keng
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- 2014
- Full Text
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4. Quality control of mitochondrial gene expression
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Ng, Kah Ying, University of Helsinki, Faculty of Biological and Environmental Sciences, Doctoral Programme in Integrative Life Science, Helsingin yliopisto, bio- ja ympäristötieteellinen tiedekunta, Integroivien biotieteiden tohtoriohjelma, Helsingfors universitet, bio- och miljövetenskapliga fakulteten, Doktorandprogrammet i integrerande biovetenskap, Rehling, Peter, and Battersby, Brendan
- Subjects
biochemistry - Abstract
Mitochondria are organelles found in all eukaryotic cells and essential for metabolic functions and cell fitness. Mammalian mitochondria contain their own genome and ribosomes to synthesize 13 proteins that are core components of oxidative phosphorylation (OXPHOS) complexes. The majorityof the mitochondrial proteome is encoded by the nuclear genome and are synthesized in the cytoplasm for transport into the organelle. Once imported into mitochondria, the 80 nuclear-encoded structural proteins assemble with the 13 mitochondrial-encoded counterparts to form multi-subunit complexes known as the OXPHOS system. Mitochondrial gene expression is the process of translating the information encoded on the mitochondrial genome into proteins that make up the OXPHOS complexes. This process involves nuclear-encoded factors and therefore requires tight coordination between mitochondrial and nuclear genome. During mitochondrial protein synthesis, nascent chains emerging from the ribosomes are inserted into the inner membrane for assembly into OXPHOS complexes and those that failed to insert or assemble into complexes are targeted for degradation. The co-translational insertion and degradation of mitochondrial nascent chain are regulated by a dedicated set of quality control machinery. Quality control of mitochondrial gene expression is a collective term for surveillance mechanisms that monitor molecular events leading to protein translation. In this dissertation, I have identified the chaperone protease complex composed of AFG3L2 subunits as the key component in co-translational quality control of mitochondrial nascent chains. AFG3L2 dysfunction triggers the activity of metalloprotease OMA1, which proteolytically process the dynamin-related GTPAse OPA1 and remodels the mitochondrial membrane morphology. Failure to counteract this stress response in a timely manner affects mitochondrial membrane dynamics and generates negative feedback on mitochondrial gene expression. My research establishes that this stress response is due exclusively to defects in quality control of mitochondrial nascent chains. Co-translational insertion of mitochondrial nascent chain is mediated by OXA1L insertase. Here, I have shown how OXA1L cooperates with AFG3L2 in regulating the insertion and turnover of mitochondrial nascent chains. In the absence of OXA1L, MT-ATP6 nascent chains are not inserted into the inner membrane and rapidly degraded by AFG3L2. These data have demonstrated how the activities of OXA1L and AFG3L2 determine the fate of a nascent chain. In addition, I have also found that translation of a specific pathogenic MT-ATP6 variant has a profound effect on mitochondrial gene expression. In the absence of AFG3L2 or OXA1L, this variant exhibits severe mitochondrial translation defect. Overall, these findings have provided new insights into the role of mitochondrial protein quality control mechanism in regulating mitochondrial gene expression. The last part of the dissertation addresses the frequency of errors at the 3' end of mitochondrial mRNAs. The human mitochondrial genome is transcribed into long polycistronic RNA transcripts that must be processed to release individual RNAs (rRNAs, tRNAs and mRNAs). Errors in the RNA processing step will generate aberrant mRNAs that interfere with the translation of fully functional proteins. To determine the error rate and diversity of aberrant mitochondrial mRNAs, a novel next generation sequencing approach was developed to provide comprehensive analysis of the 3’ end of mitochondrial transcripts. My results show the presence of aberrant mRNAs and variations in mitochondrial post-transcriptional modifications in health and disease. In addition, a significant proportion of these aberrant mRNAs lack a complete stop codon and are associated with translating mitochondrial ribosomes. Together, these observations demonstrate an inherent error rate in mitochondrial gene expression that requires quality control mechanisms to maintain functional protein synthesis. In conclusion, my thesis has identified critical steps in co-translational quality control of mitochondrial nascent chain synthesis and investigated the functional consequences of defective quality control system on mitochondrial gene expression. Mitokondriot ovat organelleja, joita esiintyy kaikissa eukaryoottisoluissa ja jotka ovat välttämättömiä aineenvaihduntatoiminnoille ja solujen kunto. Nisäkkäiden mitokondriot sisältävät oman genomin ja ribosomit syntetisoivat 13 proteiinit, jotka ovat oksidatiivisen fosforylaation (OXPHOS) kompleksien ydinkomponentteja. Suurin osa mitokondrioproteomista on ydingenomi koodaama ja syntetisoituu sytoplasmassa kuljetettavaksi organelliin. Mitokondrioihin tuotuaan 80 tuman koodaamaa rakenneproteiinia yhdistyvät 13 mitokondrioiden koodaaman vastineen kanssa muodostaen monialayksikkökomplekseja, jotka tunnetaan nimellä OXPHOS järjestelmä. Mitokondrioiden geeniekspressio on prosessi, jossa käännetään koodattu tieto mitokondrioiden genomista proteiineihin, jotka muodostavat OXPHOS-kompleksit. Tämä prosessi sisältää ydinkoodaamia tekijöitä ja vaatii siksi tiukkaa koordinointia mitokondrioiden ja ydingenomin välillä. Mitokondrioiden proteiinisynteesin aikana ribosomeista nousevat ketjut liitetään sisäkalvoon OXPHOS-komplekseiksi kokoontumista varten, ja ne, jotka eivät onnistuneet liittämään tai koota komplekseiksi, kohdennetaan hajoamiseen. Mitokondrioiden syntymässä olevan ketjun yhteistranslaatiota ja hajoamista säätelee omistettu laadunvalvontakoneisto. Mitokondrioiden geeniekspression laadunvalvonta on yhteistermi seurantamekanismeille jotka valvovat proteiinien translaatioon johtavia molekyylitapahtumia. Tässä väitöskirjassa olen tunnistanut AFG3L2-alayksiköistä koostuvan kaperoniproteaasikompleksin avainkomponentiksi mitokondrioiden syntymässä olevien ketjujen kotranslationaalisessa laadunvalvonnassa. AFG3L2 toimintahäiriö laukaisee metalloproteaasi OMA1 toiminnan, joka prosessoi proteolyyttisesti dynamiiniin liittyvää GTPAasia OPA1 ja muokkaa mitokondrioiden kalvon morfologiaa. Epäonnistuminen vastustaa tätä stressireaktiota ajoissa vaikuttaa mitokondrioiden kalvodynamiikkaan ja tuottaa negatiivista palautetta mitokondrioiden geeniekspressiosta. Tutkimukseni osoittaa, että tämä stressireaktio johtuu yksinomaan mitokondrioiden syntymässä olevien ketjujen laadunvalvonnan puutteista. OXA1L-insertaasi välittää mitokondrioiden syntymässä olevan ketjun yhteistranslationaalisen insertion. Täällä minä ovat osoittaneet, kuinka OXA1L tekee yhteistyötä AFG3L2 kanssa säädellessäsi lisäystä ja kiertoa mitokondrioiden syntymässä olevat ketjut. OXA1L puuttuessa MT-ATP6 nousevia ketjuja ei lisätä sisäkalvoon ja AFG3L2 hajottaa sen nopeasti. Nämä tiedot ovat osoittaneet, kuinka OXA1L ja AFG3L2 aktiivisuudet määräävät syntymässä olevan ketjun kohtalon. Lisäksi olen myös havainnut, että spesifisen patogeenisen MT-ATP6-variantin translaatiolla on syvällinen vaikutus mitokondrioiden geeniekspressioon. AFG3L2 tai OXA1L puuttuessa tällä variantilla on vakava mitokondrioiden translaatiovirhe. Kaiken kaikkiaan nämä havainnot ovat antaneet uusia näkemyksiä mitokondrioiden proteiinien laadunvalvontamekanismin roolista mitokondrioiden geeniekspression säätelyssä. Väitöskirjan viimeisessä osassa käsitellään virheiden esiintymistiheyttä mitokondrion 3'-päässä mRNA. Ihmisen mitokondrion genomi transkriptoidaan pitkiksi polykistronisiksi RNA-transkripteiksi joita on käsiteltävä yksittäisten RNA (rRNA, tRNA ja mRNA) vapauttamiseksi. Virheet RNA-käsittelyvaiheessa synnyttävät poikkeavia mRNA:ita, jotka häiritsevät täysin toimivien proteiinien translaatiota. Poikkeavien mitokondrioiden mRNA virhesuhteen ja monimuotoisuuden määrittämiseksi kehitettiin uusi seuraavan sukupolven sekvensointimenetelmä, joka tarjoaa kattavan analyysin mitokondrioiden transkriptien 3'-päästä. Tulokseni osoittavat poikkeavien mRNA läsnäolon ja variaatioita mitokondrioiden transkription jälkeisissä modifikaatioissa terveydessä ja sairaudessa. Lisäksi merkittävältä osalta näistä poikkeavista mRNA:ista puuttuu täydellinen lopetuskodoni ja ne liittyvät mitokondrioiden ribosomien translaatioon. Yhdessä nämä havainnot osoittavat luontaisen virhesuhteen mitokondrioiden geeniekspressiossa, joka vaatii laadunvalvontamekanismeja toiminnallisen proteiinisynteesin ylläpitämiseksi. Yhteenvetona totean, että opinnäytetyöni on tunnistanut kriittiset vaiheet yhteiskäännösten laadunvalvonnassa mitokondrioiden syntymässä olevaa ketjusynteesiä ja tutkinut viallisen toiminnallisia seurauksia mitokondrioiden geeniekspression laadunvalvontajärjestelmä.
- Published
- 2022
5. Bi-allelic variants in the mitochondrial RNase P subunit PRORP cause mitochondrial tRNA processing defects and pleiotropic multisystem presentations
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Hochberg, Irit, primary, Demain, Leigh A.M., additional, Richer, Julie, additional, Thompson, Kyle, additional, Urquhart, Jill E., additional, Rea, Alessandro, additional, Pagarkar, Waheeda, additional, Rodríguez-Palmero, Agustí, additional, Schlüter, Agatha, additional, Verdura, Edgard, additional, Pujol, Aurora, additional, Quijada-Fraile, Pilar, additional, Amberger, Albert, additional, Deutschmann, Andrea J., additional, Demetz, Sandra, additional, Gillespie, Meredith, additional, Belyantseva, Inna A., additional, McMillan, Hugh J., additional, Barzik, Melanie, additional, Beaman, Glenda M., additional, Motha, Reeya, additional, Ng, Kah Ying, additional, O’Sullivan, James, additional, Williams, Simon G., additional, Bhaskar, Sanjeev S., additional, Lawrence, Isabella R., additional, Jenkinson, Emma M., additional, Zambonin, Jessica L., additional, Blumenfeld, Zeev, additional, Yalonetsky, Sergey, additional, Oerum, Stephanie, additional, Rossmanith, Walter, additional, Yue, Wyatt W., additional, Zschocke, Johannes, additional, Munro, Kevin J., additional, Battersby, Brendan J., additional, Friedman, Thomas B., additional, Taylor, Robert W., additional, O’Keefe, Raymond T., additional, and Newman, William G., additional
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- 2021
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6. Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis
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Ng, Kah Ying, primary, Richter, Uwe, additional, Jackson, Christopher B, additional, Seneca, Sara, additional, and Battersby, Brendan J, additional
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- 2021
- Full Text
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7. Bi-allelic variants in the mitochondrial RNase P subunit PRORP cause mitochondrial tRNA processing defects and pleiotropic multisystem presentations
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Hochberg, Irit, Demain, Leigh A.M., Richer, Julie, Thompson, Kyle, Urquhart, Jill E., Rea, Alessandro, Pagarkar, Waheeda, Rodríguez-Palmero, Agustí, Schlüter, Agatha, Verdura, Edgard, Pujol, Aurora, Quijada-Fraile, Pilar, Amberger, Albert, Deutschmann, Andrea J., Demetz, Sandra, Gillespie, Meredith, Belyantseva, Inna A., McMillan, Hugh J., Barzik, Melanie, Beaman, Glenda M., Motha, Reeya, Ng, Kah Ying, O'Sullivan, James, Williams, Simon G., Bhaskar, Sanjeev S., Lawrence, Isabella R., Jenkinson, Emma M., Zambonin, Jessica L., Blumenfeld, Zeev, Yalonetsky, Sergey, Oerum, Stephanie, Rossmanith, Walter, Yue, Wyatt W., Zschocke, Johannes, Munro, Kevin J., Battersby, Brendan J., Friedman, Thomas B., Taylor, Robert W., O'Keefe, Raymond T., Newman, William G., Hochberg, Irit, Demain, Leigh A.M., Richer, Julie, Thompson, Kyle, Urquhart, Jill E., Rea, Alessandro, Pagarkar, Waheeda, Rodríguez-Palmero, Agustí, Schlüter, Agatha, Verdura, Edgard, Pujol, Aurora, Quijada-Fraile, Pilar, Amberger, Albert, Deutschmann, Andrea J., Demetz, Sandra, Gillespie, Meredith, Belyantseva, Inna A., McMillan, Hugh J., Barzik, Melanie, Beaman, Glenda M., Motha, Reeya, Ng, Kah Ying, O'Sullivan, James, Williams, Simon G., Bhaskar, Sanjeev S., Lawrence, Isabella R., Jenkinson, Emma M., Zambonin, Jessica L., Blumenfeld, Zeev, Yalonetsky, Sergey, Oerum, Stephanie, Rossmanith, Walter, Yue, Wyatt W., Zschocke, Johannes, Munro, Kevin J., Battersby, Brendan J., Friedman, Thomas B., Taylor, Robert W., O'Keefe, Raymond T., and Newman, William G.
- Abstract
Human mitochondrial RNase P (mt-RNase P) is responsible for 5' end processing of mitochondrial precursor tRNAs, a vital step in mitochondrial RNA maturation, and is comprised of three protein subunits: TRMT10C, SDR5C1 (HSD10), and PRORP. Pathogenic variants in TRMT10C and SDR5C1 are associated with distinct recessive or x-linked infantile onset disorders, resulting from defects in mitochondrial RNA processing. We report four unrelated families with multisystem disease associated with bi-allelic variants in PRORP, the metallonuclease subunit of mt-RNase P. Affected individuals presented with variable phenotypes comprising sensorineural hearing loss, primary ovarian insufficiency, developmental delay, and brain white matter changes. Fibroblasts from affected individuals in two families demonstrated decreased steady state levels of PRORP, an accumulation of unprocessed mitochondrial transcripts, and decreased steady state levels of mitochondrial-encoded proteins, which were rescued by introduction of the wild-type PRORP cDNA. In mt-tRNA processing assays performed with recombinant mt-RNase P proteins, the disease-associated variants resulted in diminished mitochondrial tRNA processing. Identification of disease-causing variants in PRORP indicates that pathogenic variants in all three subunits of mt-RNase P can cause mitochondrial dysfunction, each with distinct pleiotropic clinical presentations.
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- 2021
8. Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.
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Ng, Kah Ying, Richter, Uwe, Jackson, Christopher B, Seneca, Sara, and Battersby, Brendan J
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- 2022
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9. High prevalence of CXCR4 usage among treatment-naive CRF01_AE and CRF51_01B-infected HIV-1 subjects in Singapore
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Ng Kah Ying, Chew Kuan Kiat, Kaur Palvinder, Kwan Joe Yap, Khong Wei Xin, Lin Li, Chua Arlene, Tan Mei Ting, Quinn Thomas C, Laeyendecker Oliver, Leo Yee Sin, and Ng Oon Tek
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CXCR4 usage ,HIV-1 ,treatment-naïve ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background Recent studies suggest HIV-1 inter-subtype differences in co-receptor usage. We examined the correlation between HIV-1 subtype and co-receptor usage among treatment-naïve HIV-1 subjects in Singapore. Additionally, we investigated whether the subtype co-receptor association was influenced by stage of infection. Methods V3 sequences of HIV-1 envelope protein gp120 were obtained from 110 HIV treatment-naïve patients and genotypic co-receptor tropism determination was performed using Geno2pheno. Two false-positive rate (FPR) cut-offs, 10% and 5.75% were selected for tropism testing. Results Subtype assignment of viral strains from 110 HIV-infected individuals based on partial sequencing of HIV-1 pol, gp120 and gp41 were as follows: 27 subtype B, 64 CRF01_AE, 10 CRF51_01B, and 9 other subtypes. At FPR=10%, 10 (100%) CRF51_01B-infected subjects and 26 (40.6%) CRF01_AE-infected subjects had CXCR4-using virus, compared to 7 (25.9%) subtype B subjects and 1 (11.1%) CRF33_01B-infected subject (P < 0.001). At FPR=5.75%, 10 (100%) CRF51_01B-infected subjects and 20 (31.3%) CRF01_AE-infected subjects had CXCR4-using virus, compared to 4 (14.8%) subtype B and 1 (11.1%) CRF33_01B-infected subjects (P < 0.001). Among those with evidence of seroconversion within 2 years prior to study enrolment, 100% of CRF51_01B-infected subjects had CXCR4-using virus, independent of Geno2pheno FPR. Conclusion CRF51_01B and CRF01_AE-infected individuals have higher prevalence of CXCR4-usage compared to subtype B infected individuals. Further studies examining these differences could help optimise the use of CCR5-antagonist in populations with these subtypes, and increase our understanding of HIV-1 biology.
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- 2013
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10. Mitochondrial stress response triggered by defects in protein synthesis quality control
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Richter, Uwe, primary, Ng, Kah Ying, additional, Suomi, Fumi, additional, Marttinen, Paula, additional, Turunen, Taina, additional, Jackson, Christopher, additional, Suomalainen, Anu, additional, Vihinen, Helena, additional, Jokitalo, Eija, additional, Nyman, Tuula A, additional, Isokallio, Marita A, additional, Stewart, James B, additional, Mancini, Cecilia, additional, Brusco, Alfredo, additional, Seneca, Sara, additional, Lombès, Anne, additional, Taylor, Robert W, additional, and Battersby, Brendan J, additional
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- 2019
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11. Clinical Evaluation of a Low Cost, In-House Developed Real-Time RT-PCR Human Immunodeficiency Virus Type 1 (HIV-1) Quantitation Assay for HIV-1 Infected Patients
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Kaur, Palvinder, primary, Khong, Wei Xin, additional, Wee, Sue Yuen, additional, Tan, Eng Lee, additional, Pipper, Juergen, additional, Koay, Evelyn, additional, Ng, Kah Ying, additional, Yap, Joe Kwan, additional, Chew, Kuan Kiat, additional, Tan, Mei Ting, additional, Leo, Yee Sin, additional, Inoue, Masafumi, additional, and Ng, Oon Tek, additional
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- 2014
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12. Phylodynamic Profile of HIV-1 Subtype B, CRF01_AE and the Recently Emerging CRF51_01B among Men Who Have Sex with Men (MSM) in Singapore
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Ng, Kim Tien, primary, Ng, Kah Ying, additional, Khong, Wei Xin, additional, Chew, Kuan Kiat, additional, Singh, Palvinder Kaur, additional, Yap, Joe Kwan, additional, Tan, Mei Ting, additional, Leo, Yee Sin, additional, Laeyendecker, Oliver, additional, Quinn, Thomas C., additional, Kamarulzaman, Adeeba, additional, Tee, Kok Keng, additional, and Ng, Oon Tek, additional
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- 2013
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13. Clinical Evaluation of an In-House Human Immunodeficiency Virus (HIV) Genotyping Assay for the Detection of Drug Resistance Mutations in HIV-1 Infected Patients in Singapore
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Chew, Kuan Kiat, primary, Ng, Kah Ying, additional, Khong, Wei Xin, additional, Kaur, Palvinder, additional, Yap, Joe Kwan, additional, Chua, Arlene, additional, Tan, Mei Ting, additional, Koh, Yin Ling, additional, Thoon, Koh Cheng, additional, Leo, Yee Sin, additional, and Ng, Oon Tek, additional
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- 2012
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14. Detection and genetic characterisation of qnrB in hospital isolates of Klebsiella pneumoniae in Singapore
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Teo, Jeanette Woon Pei, primary, Ng, Kah Ying, additional, and Lin, Raymond Tzer Pin, additional
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- 2009
- Full Text
- View/download PDF
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