Identification of alternative transcripts of theTRF1/Pin2 gene

Upregulation of RNA Processing Factors in Poorly Differentiated Lung Cancer Cells

Intratumoral heterogeneity in non–small cell lung cancer (NSCLC) has been appreciated at the histological and cellular levels, but the association of less differentiated pathology with poor clinical outcome is not understood at the molecular level. Gene expression profiling of intact human tumors fails to reveal the molecular nature of functionally distinct epithelial cell subpopulations, in particular the tumor cells that fuel tumor growth, metastasis, and disease relapse. We generated primary serum-free cultures of NSCLC and then exposed them to conditions known to promote differentiation: the air-liquid interface (ALI) and serum. The transcriptional network of the primary cultures was associated with stem cells, indicating a poorly differentiated state, and worse overall survival of NSCLC patients. Strikingly, the overexpression of RNA splicing and processing factors was a prominent feature of the poorly differentiated cells and was also observed in clinical datasets. A genome-wide analysis of splice isoform expression revealed many alternative splicing events that were specific to the differentiation state of the cells, including an unexpectedly high frequency of events on chromosome 19. The poorly differentiated cells exhibited alternative splicing in many genes associated with tumor progression, as exemplified by the preferential expression of the short isoform of telomeric repeat-binding factor 1 (TERF1), also known as Pin2. Our findings demonstrate the utility of the ALI method for probing the molecular mechanisms that underlie NSCLC pathogenesis and provide novel insight into posttranscriptional mechanisms in poorly differentiated lung cancer cells.

Differential transcriptional and posttranslational transcription factor 7-like regulation among nondiabetic individuals and type 2 diabetic patients

Human genetic studies have revealed that the T minor allele of single nucleotide polymorphism rs7903146 in the transcription factor 7-like 2 (TCF7L2) gene is strongly associated with an increased risk of diabetes by 30%-40%. Molecular and clinical studies are of great importance for understanding how this unique variation in TCF7L2 influences type 2 diabetes (T2D) onset and progression. At the molecular level, some studies have been performed in diabetic mice and pancreatic islets from healthy human donors. Whereas TCF7L2 mRNA levels are up-regulated in islets, protein levels are down-regulated. We performed studies on TCF7L2 splicing, mRNA expression, and protein levels in immortalized human lymphocytes from nondiabetic individuals and T2D patients carrying the C/C or the at-risk T/T genotype. Our results show differential expression of TCF7L2 splice variants between nondiabetic and T2D patients carrying the at-risk genotype, as well as differences in protein levels. Therefore, we investigated the regulation of splice variants, and our results propose that splicing of exon 4 is under control of the serine-arginine-rich factor transformer 2 β (TRA2B). Finally, we studied the endoplasmic reticulum stress pathways, looking for a posttranslational explanation. We saw a shift in the activation of these pathways between nondiabetic individuals and T2D patients carrying the at-risk genotype. These results suggest that, in human immortalized lymphocytes carrying the at-risk T/T genotype, first the differential expression of TCF7L2 splice variants implies a regulation, at least for exon 4, by TRA2B and second, the differential protein levels between both T/T carriers point to a different activation of endoplasmic reticulum stress pathways.

Characterization of the telomere complex, TERF1 and TERF2 genes in muntjac species with fusion karyotypes

The telomere binding proteins TRF1 and TRF2 maintain and protect chromosome ends and confer karyotypic stability. Chromosome evolution in the genus Muntiacus is characterized by numerous tandem (end-to-end) fusions. To study TRF1 and TRF2 telomere binding proteins in Muntiacus species, we isolated and characterized the TERF1 and -2 genes from Indian muntjac (Muntiacus muntjak vaginalis; 2n = 6 female) and from Chinese muntjac (Muntiacus reveesi; 2n = 46). Expression analysis revealed that both genes are ubiquitously expressed and sequence analysis identified several transcript variants of both TERF genes. Control experiments disclosed a novel testis-specific splice variant of TERF1 in human testes. Amino acid sequence comparisons demonstrate that Muntiacus TRF1 and in particular TRF2 are highly conserved between muntjac and human. In vivo TRF2-GFP and immuno-staining studies in muntjac cell lines revealed telomeric TRF2 localization, while deletion of the DNA binding domain abrogated this localization, suggesting muntjac TRF2 represents a functional telomere protein. Finally, expression analysis of a set of telomere-related genes revealed their presence in muntjac fibroblasts and testis tissue, which suggests the presence of a conserved telomere complex in muntjacs. However, a deviation from the common theme was noted for the TERT gene, encoding the catalytic subunit of telomerase; TERT expression could not be detected in Indian or Chinese muntjac cDNA or genomic DNA using a series of conserved primers, while TRAP assay revealed functional telomerase in Chinese muntjac testis tissues. This suggests muntjacs may harbor a diverged telomerase sequence.