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[Display omitted] Human arylamine N-acetyltransferase 1 (NAT1) encodes a drug-metabolising enzyme that plays a role in chemical-associated cancer risk, cancer cell survival and mitochondrial function. Its expression and protein activity are regulated by transcriptional, translational, and post-translational processes, including microRNAs such as miR-1290. Several studies have shown the presence of multiple polyadenylation sites in the NAT1 gene. However, their role in NAT1 expression is poorly understood. Here, we have investigated the genetic sequence of the NAT1 gene in human cell lines, peripheral blood mononuclear cells and breast tumour tissue. We identified five potential polyadenylation signals, two of which carry known single nucleotide polymorphism that affect site usage. Cells that are homozygous for adenine at base 1642, the most distal polyadenylation site, use this site whereas those homozygous for cytosine at base 1642 could not. We also found that the presence of adenine at base 1642 is associated with the NAT1*10 haplotype. Because the putative binding site for miR-1290 is located between the last two polyadenylation sites, we hypothesised that cells that do not use the most distal site will be unaffected by miR-1290. However, this was not the case. NAT1 activity was positively correlated with miR-1290, and induction of miR-1290 in SH-SY5Y cells was associated with induction, not inhibition, of NAT1 activity. The use of PolyA1264 or PolyA1642 did not alter NAT1 activity following ectopic expression of a miR-1290 mimic. These results suggest that the role of miR-1290 in the regulation of NAT1 activity is more complex than previously reported. [ABSTRACT FROM AUTHOR]

Filamentous fungi, particularly Aspergillus species, have recently attracted attention as host organisms for recombinant protein production. Because the secretory yields of heterologous proteins are generally low compared with those of homologous proteins or proteins from closely related fungal species, several strategies to produce substantial amounts of recombinant proteins have been conducted. Codon optimization is a powerful tool for improving the production levels of heterologous proteins. Although codon optimization is generally believed to improve the translation efficiency of heterologous genes without affecting their mRNA levels, several studies have indicated that codon optimization causes an increase in the steady-state mRNA levels of heterologous genes in filamentous fungi. However, the mechanism that determines the low mRNA levels when native heterologous genes are expressed was poorly understood. We recently showed that the transcripts of heterologous genes are polyadenylated prematurely within the coding region and that the heterologous gene transcripts can be stabilized significantly by codon optimization, which is probably attributable to the prevention of premature polyadenylation in Aspergillus oryzae. In this review, we describe the detailed mechanism of premature polyadenylation and the rapid degradation of mRNA transcripts derived from heterologous genes in filamentous fungi. [ABSTRACT FROM AUTHOR]

Background: mRNA polyadenylation is an essential step of pre-mRNA processing in eukaryotes. Accurate prediction of the pre-mRNA 3'-end cleavage/polyadenylation sites is important for defining the gene boundaries and understanding gene expression mechanisms. Results: 28761 human mapped poly(A) sites have been classified into three classes containing different known forms of polyadenylation signal (PAS) or none of them (PAS-strong, PAS-weak and PAS-less, respectively) and a new computer program POLYAR for the prediction of poly(A) sites of each class was developed. In comparison with polya_svm (till date the most accurate computer program for prediction of poly(A) sites) while searching for PAS-strong poly(A) sites in human sequences, POLYAR had a significantly higher prediction sensitivity (80.8% versus 65.7%) and specificity (66.4% versus 51.7%) However, when a similar sort of search was conducted for PAS-weak and PAS-less poly(A) sites, both programs had a very low prediction accuracy, which indicates that our knowledge about factors involved in the determination of the poly(A) sites is not sufficient to identify such polyadenylation regions. Conclusions: We present a new classification of polyadenylation sites into three classes and a novel computer program POLYAR for prediction of poly(A) sites/regions of each of the class. In tests, POLYAR shows high accuracy of prediction of the PAS-strong poly(A) sites, though this program's efficiency in searching for PAS-weak and PAS-less poly(A) sites is not very high but is comparable to other available programs. These findings suggest that additional characteristics of such poly(A) sites remain to be elucidated. POLYAR program with a stand-alone version for downloading is available at http://cub.comsats.edu.pk/polyapredict.htm. [ABSTRACT FROM AUTHOR]

Rett syndrome is a severe disorder characterized by loss of acquired skills after a period of normal development in infant girls. It is caused mainly by mutations in the MECP2 gene. In this study, we reported mutations in the MECP2 gene in 7 Tunisian patients with classic Rett syndrome. The results showed the presence of a double mutation in 1 patient: p.R306C and c.1461+ 98insA, which create a new hypothetical polyadenylation site in the 3'UTR of the MECP2 gene. We also detected in another patient a new variant c.1461+ 92C>G in the 30UTR located previous to 34 bp from the polyadenylation site with a score of 4.085. This variation is located in a hypothetical splicing enhancer with a score of 1.96277 according to the ESE finder program. In the remaining 5 patients, we found 2 common mutations: p.T158M in 4 individuals and p.R168X in only 1 girl. [ABSTRACT FROM AUTHOR]