Abstract
We have isolated and characterized in detail 15 lambda Charon 4A recombinant bacteriophage containing histone genes from a chicken genomic library. Restriction enzyme-mapping analysis and Southern hybridization to sequenced, homologous histone probes indicate that these genes are not tandemly reiterated within the chicken genome; they usually reside in clusters even though there is no unique array of genes that appears to constitute a typical cluster. Chicken H4 and H1 genes were identified within the genomic recombinants and subsequently sequenced. Extensive regions of homology exist in the 5'- and 3'-flanking regions of the chicken H4 gene when compared to H4 genes from other organisms. In addition to the well documented histone-specific domains, two previously unreported regions of homology lie 5' to this gene: an octanucleotide and a pentanucleotide sequence lying 59 and 116 nucleotides upstream from the H4 gene CAP site, respectively. The H1 gene sequence predicts that the H1 polypeptide is 217 amino acids in length. The 5'-flanking domain of this gene contains, in addition to the transcriptional initiation site and the ATA box, two unusual sequences: one is a nonamer which resides 29 nucleotides upstream from the "ATA" box and is conserved in both the chicken and sea urchin H1 genes, while the other is a GC-rich repetitive sequence element. The majority of the chicken histone genes among the 15 unique lambda recombinant clones are expressed almost exclusively during in ovo development (i.e. from at least 4 days postfertilization up to hatching, about 20-21 days postfertilization) and appear not to be associated with any particular tissue type.
Highlights
From the $Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60201 and the 6DeDartment.s of Microbiolom and Public Health and Biochemistry, Michigan State University
Extensive regions of homology exist in the5’- and 3”flanking regions of the chicken H4 gene when compared to H4 genes from other organisms
This H4gene encodes a polypeptidewhose amino erase 11-transcribed genes,but inconcordance with theabove acid sequence is identical with the calf H4 protein, the uni- observationsreported for the H4 gene, thereisno typical formity of the coding sequence when compared to other H4 genes alone does not prove that it is an expressed gene
Summary
All hybridization and washing conditions used were as previously described [14, 15]. [ L Y - ~ * P ] ~ C(2T0P00 Ci/mmol; ICN) was 2.3 p ~ 50; units of RNasin (Biotec) were included to increase the average length of the cDNA transcripts [28]; and 240 units of avian myeloblastosis virus reverse transcriptase (Life Sciencesw)ere added. This mixturewas incubated at 42 "C for 60 min.
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