The Q300 gene: a novel transcription unit induced in simian virus 40-infected and -transformed mouse cells

The Q300 element is a single-copy 233-bp genomic mouse DNA fragment carrying a high-affinity binding site for the simian virus 40 (SV40) large T antigen. This element was used to screen an EMBL3 mouse genomic library. We could identify a genomic clone containing an approximately 500-bp transcribed region flanking the Q300 element. The transcribed region, termed the Q300 transcription unit or Q300 gene, is overexpressed in acutely SV40-infected or SV40-transformed mouse and rat cells. The Q300 gene includes an open reading frame which has the coding potential for a small polypeptide with an extremely hydrophobic N terminus and a hydrophilic C terminus. The deduced polypeptide has some similarity with the papillomavirus E5 oncoprotein.