Molecular cloning of cDNA and tissue‐specific expression of the gene for SII‐K1, a novel transcription elongation factor SII

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Abstract
Background: Transcription elongation factor SII has been shown to promote read‐through by RNA polymerase II of pausing sites within various eukaryotic genes in vitro by inducing cleavage of the 3′‐end of the nascent transcript in the ternary elongation complex. Recently, we showed that various mouse tissues contain multiple SII‐related proteins. Of these, ‘general SII’ was ubiquitously expressed, whereas the others were expressed in a tissue‐specific manner. We have identified testis‐specific SII (SII‐T1) and shown that it was expressed exclusively in spermatocytes.Results: A new SII cDNA clone (pSII‐K1) was isolated from mouse kidney. This clone contained an open reading frame which encoded a protein consisting of 347 amino acid residues (SII‐K1). A comparison of the amino acid sequences of SII‐K1 with those of general SII and SII‐T1 revealed that their amino‐ and carboxy‐terminal regions were very similar, but that the sequence of the 95 internal residues (87/181) was unique to each. The recombinant SII‐K1 produced in Escherichia coli stimulated RNA polymerase II as did general S‐II. The gene for SII‐K1 was found to be expressed strongly in the heart, liver, skeletal muscle and kidney, but not in other tissues examined. Contrary to the expression of the general SII gene, the SII‐K1 gene was expressed only in 15‐ and 17‐day‐old embryos during mouse embryonic development.Conclusions: We identified a novel member of SII family transcription elongation factor named SII‐K1. This factor was expressed exclusively in the heart, liver, kidney and skeletal muscle. During mouse embryonic development, no significant expression of the SII‐K1 gene was detected before the formation of these tissues.