Chromosomal position, structure, expression, and requirement of genes for chicken transcription factor IIA.

Transcription factor IIA (TFIIA) is one of the general transcription factors for RNA polymerase II and composed of three subunits, TFIIAalpha, TFIIAbeta and TFIIAgamma. TFIIAalpha and TFIIAbeta are encoded by a single gene (TFIIAalphabeta) and mature through internal cleavage of TFIIAalphabeta. In this study, we found that structures of TFIIAalphabeta and TFIIAgamma are highly homologous with each mammalian counterpart. Exon-intron organizations of the human and chicken TFIIA genes were also homologous. The sequence of the cleavage region of the chicken TFIIAalphabeta precursor protein was fitted to the consensus cleavage recognition site. It was thus demonstrated that TFIIA is conserved in vertebrates. TFIIA proteins are present ubiquitously in chicken tissues. Fluorescent in situ hybridization revealed that TFIIAalphabeta and TFIIAgamma genes are located in chromosome 5 and a mini-chromosome, respectively. We generated semi-knockout chicken DT40 cells for TFIIAalphabeta and TFIIAgamma genes with high homologous recombination efficiencies, whereas we failed to establish double-knockout cells for each gene. It is thought that both genes for TFIIA are required in vertebrates. TFIIA siRNA resulted in deceleration of cell growth rate, suggesting that, consistent with those of knockout assays, TFIIA is associated with cell growth regulation.

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