RESUMO
A locus on human chromosome 11q23 tagged by marker rs3802842 was associated with colorectal cancer (CRC) in a genome-wide association study; this finding has been replicated in case-control studies worldwide. In order to identify biologic factors at this locus that are related to the etiopathology of CRC, we used microarray-based target selection methods, coupled to next-generation sequencing, to study 103 kb at the 11q23 locus. We genotyped 369 putative variants from 1,030 patients with CRC (cases) and 1,061 individuals without CRC (controls) from the Ontario Familial Colorectal Cancer Registry. Two previously uncharacterized genes, COLCA1 and COLCA2, were found to be co-regulated genes that are transcribed from opposite strands. Expression levels of COLCA1 and COLCA2 transcripts correlate with rs3802842 genotypes. In colon tissues, COLCA1 co-localizes with crystalloid granules of eosinophils and granular organelles of mast cells, neutrophils, macrophages, dendritic cells and differentiated myeloid-derived cell lines. COLCA2 is present in the cytoplasm of normal epithelial, immune and other cell lineages, as well as tumor cells. Tissue microarray analysis demonstrates the association of rs3802842 with lymphocyte density in the lamina propria (p = 0.014) and levels of COLCA1 in the lamina propria (p = 0.00016) and COLCA2 (tumor cells, p = 0.0041 and lamina propria, p = 6 × 10(-5)). In conclusion, genetic, expression and immunohistochemical data implicate COLCA1 and COLCA2 in the pathogenesis of colon cancer. Histologic analyses indicate the involvement of immune pathways.
Assuntos
Colo/metabolismo , Neoplasias Colorretais/genética , Regulação Neoplásica da Expressão Gênica , Predisposição Genética para Doença/genética , Sistema Imunitário/metabolismo , Polimorfismo de Nucleotídeo Único , Sequência de Aminoácidos , Western Blotting , Células CACO-2 , Linhagem Celular Tumoral , Colo/patologia , Neoplasias Colorretais/metabolismo , Neoplasias Colorretais/patologia , Predisposição Genética para Doença/classificação , Células HCT116 , Células HEK293 , Células HL-60 , Células HT29 , Células HeLa , Humanos , Sistema Imunitário/patologia , Imuno-Histoquímica , Células Jurkat , Células K562 , Células MCF-7 , Dados de Sequência Molecular , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Filogenia , RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Células U937RESUMO
The sxy (tfoX) gene product is the central regulator of DNA uptake by naturally competent gamma-proteobacteria such as Haemophilus influenzae, Vibrio cholerae and probably Escherichia coli. However, the mechanisms regulating sxy gene expression are not understood despite being key to understanding the physiological role of DNA uptake. We have isolated mutations in H. influenzae sxy that greatly elevate translation and thus cause competence to develop in otherwise non-inducing conditions (hypercompetence). In vitro nuclease analysis confirmed the existence of an extensive secondary structure at the 5' end of sxy mRNA that sequesters the ribosome-binding site and start codon in a stem-loop. All of the hypercompetence mutations reduced mRNA base pairing, and one was shown to cause a global destabilization that increased translational efficiency. Conversely, mutations engineered to add mRNA base pairs strengthened the secondary structure, resulting in reduced translational efficiency and greatly reduced competence for genetic transformation. Transfer of wild-type cells to starvation medium improved translational efficiency of sxy while independently triggering the sugar starvation regulator (CRP) to stimulate transcription at the sxy promoter. Thus, mRNA secondary structure is responsive to conditions where DNA uptake will be favorable, and transcription of sxy is simultaneously enhanced if CRP activation signals that energy supplies are limited.
