A frequent TG deletion near the polyadenylation signal of the human HEXB gene: occurrence of an irregular DNA structure and conserved nucleotide sequence motif in the 3' untranslated region

Intronic cleavage and polyadenylation regulates gene expression during DNA damage response through U1 snRNA

The DNA damage response involves coordinated control of gene expression and DNA repair. Using deep sequencing, we found widespread changes of alternative cleavage and polyadenylation site usage on ultraviolet-treatment in mammalian cells. Alternative cleavage and polyadenylation regulation in the 3ʹ untranslated region is substantial, leading to both shortening and lengthening of 3ʹ untranslated regions of genes. Interestingly, a strong activation of intronic alternative cleavage and polyadenylation sites is detected, resulting in widespread expression of truncated transcripts. Intronic alternative cleavage and polyadenylation events are biased to the 5ʹ end of genes and affect gene groups with important functions in DNA damage response and cancer. Moreover, intronic alternative cleavage and polyadenylation site activation during DNA damage response correlates with a decrease in U1 snRNA levels, and is reversible by U1 snRNA overexpression. Importantly, U1 snRNA overexpression mitigates ultraviolet-induced apoptosis. Together, these data reveal a significant gene regulatory scheme in DNA damage response where U1 snRNA impacts gene expression via the U1-alternative cleavage and polyadenylation axis.

Is the Expression of Androgen Receptor Protein Associated With the Length of AC Repeats in the Type III 5-α Reductase Gene in Prostate Cancer Patients?

Purpose

Type III 5-α reductase (SRD5A3; steroid 5-α reductase 3) may be associated with the progression of prostate cancer (PCa). The aim of our study was to determine whether the length of AC repeats in the SRD5A3 gene is associated with the risk of PCa and the expression of androgen receptor (AR) protein in Korean men.

Materials and Methods

We compared the length of AC repeats in the short tandem repeat (STR) region of the SRD5A3 gene in 68 PCa patients and 81 control subjects by genotyping. A total of 55 patients in the PCa group underwent radical prostatectomy. We evaluated the expression of AR protein by using Western blotting and tested the association between the type of AC repeats in the SRD5A3 gene and AR protein expression and clinical and pathologic parameters.

Results

The short type of STR had less than 21 copies of AC repeats in the SRD5A3 gene. The SS type (short and short type) of STR of the SRD5A3 gene was 2.2 times as likely to occur in PCa patients as in controls (odds ratio, 2.21; 95% confidence interval, 1.14 to 4.31; p=0.019). However, AC repeats of the SRD5A3 gene were not associated with AR protein expression or clinical or pathologic parameters in PCa samples.

Conclusions

These results suggest that the short AC repeats of SRD5A3 polymorphism are associated with an increased risk of PCa. SRD5A3 polymorphism may contribute to a genetic predisposition for PCa.

Integrated multiplex ligation dependent probe amplification (MLPA) assays for the detection of alterations in the HEXB, GM2A and SMARCAL1 genes to support the diagnosis of Morbus Sandhoff, M. Tay-Sachs variant AB and Schimke immuno-osseous dysplasia in humans

Multiplex ligation dependent probe amplification (MLPA) assays were designed for the genes HEXB (OMIM: 606873), GM2A (OMIM: 613109) and SMARCAL1 (OMIM: 606622) of humans. Two sets of synthetic MLPA probes for these coding exons were tested. Changes in copy numbers were detected as well as single nucleotide polymorphisms (SNPs) by complementary DNA sequence analyses. The MLPA method was shown to be reliable for mutation detection and identified five published and 12 new mutations. In all cases from a Morbus Sandhoff cohort of patients, exclusively one variation in copy number was observed and linked to a nucleotide alteration called c.1614-14C>A. This deletion comprised exons 1-5. One of these cases is described in detail. Deletions were neither detected in the GM2A nor the SMARCAL1 genes. The MLPA assays complement routine diagnostics for M. Sandhoff (OMIM: 268800), M. Tay-Sachs variant AB (OMIM: 272750) and Schimke immuno-osseous dysplasia (OMIM: 242900).

Molecular and functional analysis of the HEXB gene in Italian patients affected with Sandhoff disease: identification of six novel alleles

We report the molecular characterization of 12 unrelated Italian patients affected with Sandhoff disease (SD), a recessively inherited disorder caused by mutations in HEXB gene. We identified 11 different mutations of which six are novel: one large deletion of 2,406 nt, (c.299+1471_408del2406), one frameshift mutation c.965delT (p.I322fsX32), one nonsense c.1372C>T (p.Q458X), and three splicing mutations (c.299G>T, c.300-2A>G and c.512-1G>T). One allele was only characterized at the messenger RNA (mRNA) level (r = 1170_1242del). Real-time polymerase chain reaction analysis of the HEXB mRNA from fibroblasts derived from patients carrying the novel point mutations showed that the presence of the premature termination codon in the transcript bearing the mutation c.965delT triggers the nonsense-mediated decay (NMD) pathway, which results in the degradation of the aberrant mRNA. The presence of the c.299G>T mutation leads to the degradation of the mutated mRNA by a mechanism other than NMD, while mutations c.300-2A>G and c.512-1G>T cause the expression of aberrant transcripts. In our group, the most frequent mutation was c.850C>T (p.R284X) representing 29% of the alleles. Haplotype analysis suggested that this mutation did not originate from a single genetic event. Interestingly, the common 16-kb deletion mutation was absent. This work provides valuable information regarding the molecular genetics of SD in Italy and provides new insights into the molecular basis of the disease.

The 3' processing factor CstF functions in the DNA repair response

Following DNA damage, mRNA levels decrease, reflecting a coordinated interaction of the DNA repair, transcription and RNA processing machineries. In this study, we provide evidence that transcription and polyadenylation of mRNA precursors are both affected in vivo by UV treatment. We next show that the polyadenylation factor CstF, plays a direct role in the DNA damage response. Cells with reduced levels of CstF display decreased viability following UV treatment, reduced ability to ubiquitinate RNA polymerase II (RNAP II), and defects in repair of DNA damage. Furthermore, we show that CstF, RNAP II and BARD1 are all found at sites of repaired DNA. Our results indicate that CstF plays an active role in the response to DNA damage, providing a link between transcription-coupled RNA processing and DNA repair.

A systematic analysis of disease-associated variants in the 3' regulatory regions of human protein-coding genes II: the importance of mRNA secondary structure in assessing the functionality of 3' UTR variants

In an attempt both to catalogue 3' regulatory region (3' RR)-mediated disease and to improve our understanding of the structure and function of the 3' RR, we have performed a systematic analysis of disease-associated variants in the 3' RRs of human protein-coding genes. We have previously analysed the variants that have occurred in two specific domains/motifs of the 3' untranslated region (3' UTR) as well as in the 3' flanking region. Here we have focused upon 83 known variants within the upstream sequence (USS; between the translational termination codon and the upstream core polyadenylation signal sequence) of the 3' UTR. To place these variants in their proper context, we first performed a comprehensive survey of known cis-regulatory elements within the USS and the mechanisms by which they effect post-transcriptional gene regulation. Although this survey supports the view that RNA regulatory elements function within the context of specific secondary structures, there are no general rules governing how secondary structure might exert its influence. We have therefore addressed this question by systematically evaluating both functional and non-functional (based upon in vitro reporter gene and/or electrophoretic mobility shift assay data) USS variant-containing sequences against known cis-regulatory motifs within the context of predicted RNA secondary structures. This has allowed us not only to establish a reliable and objective means to perform secondary structure prediction but also to identify consistent patterns of secondary structural change that could potentiate the discrimination of functional USS variants from their non-functional counterparts. The resulting rules were then used to infer potential functionality in the case of some of the remaining functionally uncharacterized USS variants, from their predicted secondary structures. This not only led us to identify further patterns of secondary structural change but also several potential novel cis-regulatory motifs within the 3' UTRs studied.

Short tandem repeat (STR) replacements in UTRs and introns suggest an important role for certain STRs in gene expression and disease

Some untranslated sequence (UTR)-localized, short tandem repeats (STRs) exhibit evidence of selection pressure, including STR-coupling preferences, STR conservation, interspecies STR-STR replacements, and STR variants implicated in certain diseases. We wished to determine if STR replacements occurred near disease-related genes, including previously unstudied STRs as well as some STRs already implicated in disease. Among nine strong-candidate prostate cancer (CaP)-predisposing genes, three [steroid 5-alpha-reductase 2 (Srd5A-2), macrophage scavenger receptor-1 (MSR-1), and tumor necrosis factor receptor-21 (Tnfr-21)] exhibited striking STR replacements (P<0.001). The glomerular disease-related gene, CD2AP, exhibited an STR replacement flanked by well-conserved sequences, suggesting an STR-focused process. Another glomerular disease-related gene, rabphilin 3A, exhibited at least two STR replacements at the same UTR position comparing Drosophila melanogaster, Mus musculus, and Homo sapiens. Two genes implicated in blood-clotting disorders, von Willebrand factor (vWA) and fibrinogen alpha (FGA), exhibited multiple-intron STR replacements among mammals, extending STR replacement phenomena to introns. Among primates, a tyrosine hydroxylase (THO1) intron STR, previously implicated in both schizophrenia and drug withdrawal delirium, exhibited frequent replacements. Some STR replacements were early events in gene divergence. When STR sequences of closely related species were available, STR replacement was observed to be nearly as rapid as speciation. STR replacements expand the list of STR sequences that may contribute to genetic activity and to disease processes.

Short tandem repeats are associated with diverse mRNAs encoding membrane-targeted proteins

Within the genomes of multicellular organisms, short tandem repeating sequences (STRs) are ubiquitous, yet usage patterns remain obscure. The repeats (AC)n and (GU)n appear frequently in the untranslated regions (UTRs) of messenger RNAs (mRNAs). To investigate STR usage patterns, we used three approaches: (1) comparisons of individual mRNA database sequences including annotations and linked references, (2) statistical analysis of complete, UTR databases and (3) study of a large gene family, the aquaporins. Among 500 (AC)n- or (GU)n-containing mRNAs, 58 (12%) had known functions. Of these, 50 (86%) encoded proteins whose activities involved membranes or lipids, including integral membrane proteins, peripheral membrane proteins, ion channels, lipid enzymes, receptors and secreted proteins. A control sequence (AU)n also occurred in mRNAs, but only 5% encoded membrane-related functions. Investigation of all reported 3' UTR sequences, demonstrated that the STR (AC)n was 9 times more common in mRNAs encoding membrane functions than in the total UTR database (P < 0.001). Similarly, (GU)n was 8 times more common in membrane-function mRNAs than in the total database (P < 0.001). These observations suggest that (AC)n and (GU)n may be UTR signals for some mRNAs encoding membrane-targeted proteins.

Simple repeat replacements support similar functions of distinct repeats in inter-species mRNA homologs

Simple repeats are ubiquitous in metazoan genomes, but function has been elusive. We reported that distinct, short tandem repeats (STRs) were coupled with rigorous polarity and register, suggesting order in simple repeat usage. Several STRs that lacked internal, canonical base pairs were associated with mRNAs encoding membrane functions and transcription factors. We hypothesized that diverse, simple repeats, such as (AC)n, (GU)n, (AG)n, (CU)n and (CUUU)n, had similar functions. The hypothesis predicts that closely related mRNAs would sometimes exhibit STR replacements. Comparing aquaporin 3 mRNAs, in rodents and humans, (GU)20 replaced (AG)29. Comparing biglycan mRNAs, (GU)25 replaced (CA)12. Comparing immunoglobulin superfamily member 9 mRNAs, the STR-couple, (CU)17(GU)9 replaced the STR-couple, (GU)19(GC)4. Comparing tumor necrosis factor receptor-21 mRNAs, (GU)24 replaced (CUUU)16. In a collection of 52 rodent-H. sapiens homologous mRNAs that had STRs, six (11.5%) STR-STR replacements occurred, significantly more than expected based on an STR frequency of 0.13% in all reported UTRs (p<0.001). Database studies and the observation of STR replacements among transcript homologs independently support the hypothesis that diverse repeat sequences, such as (AG)n, (AC)n, (GU)n, (CU)n and (CUUU)n, have similar usage that is consistent with analogous functions.

Transcribed short tandem repeats occur in couples with strongly preferred registers

Short tandem repeats (STRs) have been widely observed, but most STRs have no recognized organization or function. Here we show that for diverse mRNAs, 84% of (GC)(n) repeats were found unexpectedly coupled with another STR, (GU)(n). These STR couples exhibited preferred polarity and register. In 3(') untranslated mRNA sequences (UTRs) 100% of (GC)(n>6) repeats were tightly coupled with (GU)(n). For (GC)(n), stem folding energy correlated with the length and number of neighboring, non-folding (GU)(n) partners (p=0.014). Approximately 20% of (AU)(n>/=14) repeats were coupled with (GU)(n). The STR couple (AC)(n)(AG)(n) also exhibited polarity and register preferences. The sequence arrangement at STR-couple joints was conserved rigorously, suggesting that these sequences were under selection pressure. Some STR couples may function as mRNA processing landmarks, based on alternative transcript comparisons. These observations suggest that some transcribed STRs may be functional UTR signals with predictable organization and usage patterns.