Identification of the cis-elements required for transcriptional control of the Chinese hamster ovary APRT gene

Abstract

Transcriptional regulation of the Chinese hamster ovary (CHO) adenine phosphoribosyltransferase-encoding gene (APRT) was studied. The 5′ region of the CHO APRT is G+C-rich, but lacking TATA or CCAAT boxes. RNase protection assays indicate that it contains multiple transcription start points ( tsp). A tsp 64 bp upstream from the translation start codon is denoted as + 1. Linker-scanning (LS) mutation analysis indicates that the −33 to + 19 region is important in regulating APRT transcription. Mutations in the −23 to −14 region abolish transcription initiated from the −23 downstream region. An unidentified protein complex binds to this region. Three Spl-binding sites are found in the APRT promoter; however, mutations of the Sp1-binding sites do not reduce APR T transcription. Mutations at two putative GCF-binding sites increase levels of transcription.