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.
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.
Tanaka
M
M
Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA.
Hennebold
J D
JD
Macfarlane
J
J
Adashi
E Y
EY
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D004622:Embryo, Mammalian / Q000502:physiology; D005260:Female; D015723:Gene Library; D006657:Histones / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017403:In Situ Hybridization; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization / Q000379:methods; D009865:Oocytes / Q000378:metabolism*; D010053:Ovary / Q000033:anatomy & histology / Q000502:physiology; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment
C423383:H1f8 protein, mouse; D006657:Histones; D011506:Proteins; D012333:RNA, Messenger