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A genomic clone for a member of the mouse type I hair keratin protein family has been isolated and analyzed in order to study the regulation of this keratin during the hair growth cycle. The coding sequence is divided into seven exons. The gene structure is typical of keratins in particular and intermediate filaments in general in that the intron-exon borders are not located at the domain borders of the protein. Comparison with a sheep wool keratin gene shows that the splice sites in the two hair keratin genes are found at identical locations relative to the amino acid sequence of the proteins. Similarly, comparison of the promoter areas of these genes shows several areas of nucleotide sequence conservation, including the area around the TATA box and an SV40 core enhancer sequence. In addition, a high degree of sequence identity exists in the fourth intron. In situ hybridization shows that transcripts of this gene are first found in the relatively undifferentiated proximal cortex area in the keratogenous zone of mouse vibrissae.

Inhibition of protein synthesis by cycloheximide or puromycin specifically increases the amount of translatable histone mRNA in exponentially growing and in synchronous G1 HeLa cells by 5-fold in 3 hours. In this case histone gene expression is uncoupled from DNA replication. We conclude that the level of histone mRNA is regulated by a labile protein and is only indirectly dependent on DNA synthesis.

A rapid reversed-phase high-performance liquid chromatography procedure for the fractionation of histones from S49 mouse lymphoma cells is reported. The system utilizes a Vydac C4 macroporous column, heptafluorobutyric acid as solubilizing and ion-pairing agent, and an acetonitrile gradient. All five histone classes and several subclass species are separated, including two H1 species, H2B, two H2A species, H4, and two H3 species. Analytical to multimilligram semipreparative scale fractionations are demonstrated while maintaining resolution of all histone types.