Mutagenesis of conserved 5' elements and transcription of a chicken H1 histone gene.

In addition to readily identifiable TATA and CAAT boxes, chicken H1 histone genes contain a highly conserved G-rich region at about minus 80 and an A-rich H1 histone gene-specific motif some 120 bases upstream from the H1 mRNA cap site. The level of transcription from wild-type, 'G-box' and 'A-box' H1 deletion mutant templates was tested in Xenopus oocytes and in HeLa cells. Removal of the H1 gene-specific motif had no effect on H1 gene transcription in either assay system, whereas deletion of the G-rich sequence decreased H1 mRNA levels by about ten-fold in oocytes and in HeLa cells. At least in heterologous systems, the H1-gene specific A-rich region does not appear to influence the level of H1 gene transcription.