A mammalian oocyte-specific linker histone gene H1oo: homology with the genes for the oocyte-specific cleavage stage histone (cs-H1) of sea urchin and the B4/H1M histone of the frog

• Published in: Development (Cambridge) Vol. 128; no. 5; pp. 655 - 664
• Main Authors: Tanaka, M, Hennebold, J D, Macfarlane, J, Adashi, E Y
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Limited 01.03.2001
• Subjects: Amino Acid Sequence; Animals; Anura; Base Sequence; Blotting, Western; double prime Hloo protein; Echinoidea; Embryo, Mammalian - physiology; Female; Gene Library; Histones - chemistry; Histones - genetics; Histones - metabolism; In Situ Hybridization; Mice; Mice, Inbred C57BL; Microscopy, Fluorescence; Molecular Sequence Data; Nucleic Acid Hybridization - methods; Oocytes - metabolism; Ovary - anatomy & histology; Ovary - physiology; Proteins - chemistry; Proteins - genetics; Proteins - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Alignment
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.128.5.655

Oocytes and early embryos of multiple (non-mammalian) species lack the somatic form of the linker histone H1. To the best of our knowledge, a mammalian oocyte-specific linker (H1) histone(s) has not, as yet, been reported. We have uncovered the cDNA in question in the course of a differential screening (suppression subtractive hybridization (SSH)) project. Elucidation of the full-length sequence of this novel 1.2 kb cDNA led to the identification of a 912 bp open reading frame. The latter encoded a novel 34 kDa linker histone protein comprised of 304 amino acids, tentatively named H1oo. Amino acid BLAST analysis revealed that H1oo displayed the highest sequence homology to the oocyte-specific B4 histone of the frog, the respective central globular (putative DNA binding) domains displaying 54% identity. Substantial homology to the cs-H1 protein of the sea urchin oocyte was also apparent. While most oocytic mRNAs corresponding to somatic linker histones are not polyadenylated (and remain untranslated), the mRNAs of (non-mammalian) oocyte-specific linker histones and of mammalian H1oo, are polyadenylated, a process driven by the consensus signal sequence, AAUAAA, detected in the 3′-untranslated region of the H1oo cDNA. Our data suggest that the mouse oocyte-specific linker histone H1oo (1) constitutes a novel mammalian homolog of the oocyte-specific linker histone B4 of the frog and of the cs-H1 linker histone of the sea urchin; (2) is expressed as early as the GV (PI) stage oocyte, persisting into the MII stage oocyte, the oocytic polar bodies, and the two-cell embryo, extinction becoming apparent at the four- to eight-cell embryonic stage; and (3) may play a key role in the control of gene expression during oogenesis and early embryogenesis, presumably through the perturbation of chromatin structure.