Abigail L. Savage

mRNA splicing and export plays a key role in the regulation of gene expression, with recent evidence suggesting an additional layer of regulation of gene expression and cellular function through the selective splicing and export of genes within specific pathways. Here we describe a role for the RNA processing factors THRAP3 and BCLAF1 in the regulation of the cellular DNA damage response (DDR) pathway, a key pathway involved in the maintenance of genomic stability and the prevention of oncogenic transformation. We show that loss of THRAP3 and/or BCLAF1 leads to sensitivity to DNA damaging agents, defective DNA repair and genomic instability. Additionally, we demonstrate that this phenotype can be at least partially explained by the role of THRAP3 and BCLAF1 in the selective mRNA splicing and export of transcripts encoding key DDR proteins, including the ATM kinase. Moreover, we show that cancer associated mutations within THRAP3 result in deregulated processing of THRAP3/BCLAF1-regulated transcripts and consequently defective DNA repair. Taken together, these results suggest that THRAP3 and BCLAF1 mutant tumors may be promising targets for DNA damaging chemotherapy.

Experiments were carried out to assess the susceptibility of normal and inflammatory bowel disease rectal mucus to desulphation and desialation by faecal extracts and by bacterial sialidase. The effects were assessed histochemically using a combined high iron diamine (HID) and alcian blue (AB) stain for sulphomucins and sialomucins. Rectal mucus in biopsies from controls (irritable bowel syndrome) and patients with ulcerative colitis or Crohn's disease was resistant to desialation by Clostridium perfringens sialidase, but susceptible to desialation and desulphation by bacteria-free extracts of normal faeces. Periodic acid-Schiff (PAS) staining of adjacent sections similarly treated showed retention of neutral mucus. One faecal extract selectively desulphated all 42 biopsies, causing the goblet cells to change from HID positive to AB positive, suggesting that most, or all HID positive cells also contain sialomucins. This alters the interpretation of previous histochemical studies. Faecal extracts from patients with active ulcerative colitis (n = 6) had desialating and desulphating effects similar to faecal extracts from normal subjects (n = 6). Ulcerative colitis (n = 21), Crohn's disease (n = 18), and control (irritable bowel syndrome) (n = 17) rectal biopsies all showed similar susceptibility to desulphation by a pooled normal faecal extract, but rectal biopsies from patients with Crohn's disease proved more resistant to desialation than control or ulcerative colitis biopsies (p less than 0.02). These studies imply that colonic mucus undergoes continual desulphation and desialation in vivo as a result of faecal enzyme activity that is probably mainly of bacterial origin. Altered susceptibility of colonic mucus to this may be important in the pathogenesis of colonic disease.

BACKGROUND: Retrotransposons are a major component of the human genome constituting as much as 45%. The hominid specific SINE-VNTR-Alus are the youngest of these elements constituting 0.13% of the genome; they are therefore a practical and amenable group for analysis of both their global integration, polymorphic variation and their potential contribution to modulation of genome regulation. RESULTS: Consistent with insertion into active chromatin we have determined that SVAs are more prevalent in genic regions compared to gene deserts. The consequence of which, is that their integration has greater potential to have affects on gene regulation. The sequences of SVAs show potential for the formation of secondary structure including G-quadruplex DNA. We have shown that the human specific SVA subtypes (E-F1) show the greatest potential for forming G-quadruplexes within the central tandem repeat component in addition to the 5' 'CCCTCT' hexamer. We undertook a detailed analysis of the PARK7 SVA D, located in the promoter of the PARK7 gene (also termed DJ-1), in a HapMap cohort where we identified 2 variable number tandem repeat domains and 1 tandem repeat within this SVA with the 5' CCCTCT element being one of the variable regions. Functionally we were able to demonstrate that this SVA contains multiple regulatory elements that support reporter gene expression in vitro and further show these elements exhibit orientation dependency. CONCLUSIONS: Our data supports the hypothesis that SVAs integrate preferentially in to open chromatin where they could modify the existing transcriptional regulatory domains or alter expression patterns by a variety of mechanisms.

A technique for lectin-peroxidase histochemistry was adapted for the study of formalin fixed paraffin embedded colonic tissue. Ten lectins with differing carbohydrate binding specificity were tested against 20 normal rectal biopsy specimens and tissue from 19 colonic carcinomata, 19 tubular or tubulovillous adenomata, and 19 hyperplastic polyps. None of the normal rectal biopsy specimens bound the lectins peanut agglutinin (PNA), Griffonia simplicifolia II (GSII), and Ulex europaeus I (UEAI), whereas 18 carcinomata, 12 adenomata, and 18 hyperplastic polyps showed affinity for one or more of these lectins. Hyperplastic colonic polyps are shown to possess similar abnormalities in glycoprotein structure to malignant and adenomatous colonic tissue. This may simply indicate a non-specific reaction to changed rates of cell proliferation but might represent a more fundamental association between hyperplastic polyps and adenocarcinomas.