Volume 272, Number 6,
Issue of February 7, 1997
pp. 3606-3614
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
Molecular Characterization of p62, a Mitotic Apparatus Protein
Required for Mitotic Progression
(Received for publication, July 2, 1996, and in revised form, November 7, 1996)
Xiaojian
Ye
and
Roger D.
Sloboda
From the Department of Biological Sciences, Dartmouth College,
Hanover, New Hampshire 03755 and the Marine Biological Laboratory,
Woods Hole, Massachusetts 02543
A 62-kDa (p62) mitotic apparatus-associated
protein is important for the proper progression of mitosis in sea
urchin embryos (Dinsmore, J. H., and Sloboda, R. D. (1989)
Cell 53, 769-780). We have isolated and characterized a
full-length p62 cDNA of 3374 base pairs which encodes an extremely
acidic polypeptide of 411 amino acids having a calculated
Mr of 46,388 and a pI of 4.01; p62 is a unique
protein with no significant identity to any known proteins. Southern
and Northern blot analyses demonstrate that the gene for p62 is present
once in the sea urchin genome and the corresponding mRNA is present
in unfertilized eggs and in early embryos through and up to the
gastrula stage. Sequence analysis suggests certain regions may
participate in chromatin association and microtubule binding, an
observation that is consistent with previous immunological data (Ye,
X., and Sloboda, R. D. (1995) Cell Motil. Cytoskeleton 30, 310-323) as well as data reported herein. Confocal microscopy reveals
that during interphase the protein binds to chromatin in the nuclei of
sea urchin eggs. In the germinal vesicles of clam oocytes at prophase
of meiosis I, p62 binds to the condensed chromosomes. Currently,
truncated clones of p62 are being used to identify the tubulin and
chromatin binding domains.