J Biol Chem, Vol. 273, Issue 38, 24654-24659, September 18, 1998
Dictyostelium TRFA Homologous to Yeast Ssn6 Is
Required for Normal Growth and Early Development
Junichi
Saito,
Takahide
Kon,
Akira
Nagasaki,
Hiroyuki
Adachi, and
Kazuo
Sutoh
From the Department of Life Sciences, Graduate School of Arts and
Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku,
Tokyo 153, Japan
The TPR (tetratricopeptide repeat) family became
widespread during evolution, having been found from bacteria to
mammals. By means of restriction enzyme-mediated integration, we have
identified a Dictyostelium gene (trfA) highly
homologous to a Saccharomyces cerevisiae gene encoding a
TPR protein, Ssn6 (Cyc8), which functions as a global transcriptional
repressor for diverse genes. The deduced amino acid sequence of the
Dictyostelium gene product, TRFA, contains 10 consecutive
TPR units as well as Gln repeats, Asn repeats, and a region rich in
Glu, Lys, Ser, and Thr. The sequences of some of the 10 TPR units in
TRFA are more than 70% identical to the corresponding units in
Ssn6.
The trfA
cells produced smooth plaques on a
bacterial lawn and failed to aggregate normally when starved on a plain
agar plate. Individual trfA
cells also failed
to correctly respond to cAMP, although the adenylyl cyclase of
trfA
cells was expressed upon starvation and
activated by stimulation with cAMP as in the wild-type cells. When
cultured in a rich medium in suspension, they grew more slowly and
stopped growing at a lower density than the wild-type cells.
Furthermore, they divided into cells of various sizes and tended to be
much smaller than the wild-type cells. These pleiotropic defects of the
trfA
cells suggest the possibility that
Dictyostelium TRFA may regulate the transcription of
diverse genes required for normal growth and early development.
Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc.