A functional variable number of tandem repeats is located at the 5' flanking region of the human secretin gene plays a downregulatory role in expression

Complex transcriptional control of the AZFa gene DDX3Y in human testis

The human DEAD-box Y (DBY) RNA helicase (aka DDX3Y) gene is thought to be the major azoospermia factor a (AZFa) gene in proximal Yq11. Men with its deletion display no somatic pathologies, but suffer from complete absence of germ cells. Accordingly, DDX3Y protein is expressed only in the germline in spermatogonia, although the transcripts were found in many tissues. Here, we show the complex transcriptional control of a testis-specific DDX3Y transcript class with initiation at different sites upstream of the gene’s open reading frame (5′Untranslated Region; UTR) and with polyadenylation in their proximal 3′UTR. The most distal transcriptional start site (TSS; ∼1 kb upstream) was mapped in MSY2, a Y-specific minisatellite. As this testis-specific 5′UTR was subsequently processed by three alternative splicing events, it has been tentatively designated ‘exon-T’(estis). The MSY2 sequence unit was also found upstream of the mouse Ddx3y gene. However, only after its tandem amplification on the Y chromosome of Platyrrhini (new world monkeys) and Catarrhini (old world monkeys) did MSY2 become part of a novel distal promoter for DDX3Y expression in testis tissue and provides a second transcriptional start site (T-TSS-II) in Catarrhini. We therefore suggest that the development of a novel distal DDX3Y promoter in primates, which is activated only in testis tissue, is probably part of the gene’s germline translation control.

Impact of copy number of distinct SV40PolyA segments on expression of a GFP reporter gene

The presence of Alu repeats downregulates the expression of the green fluorescent protein (GFP) gene. We found that SV40PolyA (PolyA, 240 bp), in either orientation, eliminated the inhibition of GFP gene expression induced by Alu repeats when it was placed between the GFP gene and the Alu repeats. In this study, 4 different segments (each 60 bp) were amplified from antisense PolyA (PolyAas) by PCR, and inserted upstream of Alu14 in pAlu14 plasmid (14 Alu repeats inserted downstream of the GFP gene in vector pEGFP-C1 in a head-tail tandem manner). Segments 1F1R (the first 60 bp segment at the 5' end of PolyAas) and 4F4R (the fourth 60 bp segment from the 5' end of PolyAas) did not activate GFP gene expression, whereas 2F2R and 3F3R (the middle two segments) did (as detected by Northern blot analysis and fluorescent microscopy). Different copy numbers of 2F2R and 3F3R segments, in a head and tail tandem manner, were inserted downstream of the GFP gene in pAlu14. p2F2R*4-Alu28, p3F3R*4-Alu18 and p3F3R*4-Alu28 were used as length controls to verify that the decrease in the expression of GFP was not due to the increased length of the inserted segment in the expression vectors. We found that 2 and 4 copies of 2F2R or 3F3R activated the GFP gene more strongly than one copy of them. However, more than 8 copies of 2F2R or 3F3R reduced the activation of the GFP gene. We concluded that SV40PolyAas contained at least two gene-activating elements (2F2R and 3F3R) and 2-4 copies of 2F2R or 3F3R were optimal for the expression of the GFP gene.

Comparative analysis of secreted enzymes between the anthropophilic-zoophilic sister species Trichophyton tonsurans and Trichophyton equinum

Trichophyton tonsurans (TT) and Trichophyton equinum (TE) are two closely related dermatophytes with very different host preferences. This study was designed to examine the genetic and transcript level variations of secreted enzymes between TT and TE. Thirty-one genes representing 10 gene families were selected for comparison and complete genomic and cDNA sequences were elucidated. Sequence analyses of the selected genes identified 104 polymorphisms between the two dermatophytes, 37 of which are expected to encode changes in their polypeptide sequence. Quantitative RT-PCR was used to examine the differences in levels of transcript between TT and TE grown over 14d in aqueous keratin medium. Differences in transcript expression between TT and TE were gene specific and ranged from 1.1-fold to 33-fold. Intra-specific variability across all genes ranged from 41% to 250%. Despite their overall genetic similarity, TT and TE exhibit a moderate degree of variability in the genomic make-up of their secreted enzymes and the extent to which they are transcribed when grown in an aqueous keratin medium. Such differences may contribute to how these genetically similar organisms have adapted to infect divergent host organisms.

ATM and ATR protect the genome against two different types of tandem repeat instability in Fragile X premutation mice

Expansion of a tandem repeat tract is responsible for the Repeat Expansion diseases, a group of more than 20 human genetic disorders that includes those like Fragile X (FX) syndrome that result from repeat expansion in the FMR1 gene. We have previously shown that the ATM and Rad3-related (ATR) checkpoint kinase protects the genome against one type of repeat expansion in a FX premutation mouse model. By crossing the FX premutation mice to Ataxia Telangiectasia-Mutated (Atm) mutant mice, we show here that ATM also prevents repeat expansion. However, our data suggest that the ATM-sensitive mechanism is different from the ATR-sensitive one. Specifically, the effect of the ATM deficiency is more marked when the premutation allele is paternally transmitted and expansions occur more frequently in male offspring regardless of the Atm genotype of the offspring. The gender effect is most consistent with a repair event occurring in the early embryo that is more efficient in females, perhaps as a result of the action of an X-linked DNA repair gene. Our data thus support the hypothesis that two different mechanisms of FX repeat expansion exist, an ATR-sensitive mechanism seen on maternal transmission and an ATM-sensitive mechanism that shows a male expansion bias.