H2A.F: an extremely variant histone H2A sequence expressed in the chicken embryo.

A cDNA clone bank has been constructed from chicken embryonic RNA. Clones hybridizing poorly to embryonic histone gene probes were selected as possible variant gene transcripts. The DNA sequence of one cDNA predicts an extremely variant H2A protein (H2A.F), which is 40% divergent from the most abundant H2A protein in chicken erythrocyte chromatin. The H2A.F gene is not highly conserved across large species barriers, but in the chicken there may be a family of linked genes. The H2A.F mRNA is approximately equal to 820 base pairs in length and, unlike most other histone mRNAs, is polyadenylylated. Significantly, the H2A.F transcript shows a limited tissue distribution in the chicken embryo.