Protein Determinants of RNA Binding by DNA Polymerase
of the T4-related Bacteriophage RB69*
Vasiliy M.
Petrov
,
San-san
Ng§, and
Jim D.
Karam
¶
From the
Department of Biochemistry, Tulane
University Health Sciences Center, New Orleans, Louisiana 70112
DNA polymerase (gp43) of phage T4 plays two
biological roles, one as an essential DNA binding replication enzyme
and the other as an mRNA-specific autogenous translational
repressor. Binding of T4 gp43 to its mRNA target (translational
operator RNA) interferes with gp43-DNA interactions, but it is unclear
how the protein determinants for binding DNA are affected by the
dynamics of gp43-mRNA interactions. We have used RB69 gp43, a
natural variant of the T4 enzyme whose crystal structure has been
determined to identify protein sites that respond to the interaction
with specific RNA. We used protein phosphorylation markers,
photocross-linking studies, protease sensitivity assays, and mutational
analyses to examine the effects of operator RNA on the enzyme's five
structural domains (N, exo, palm, fingers, and thumb). Our studies
suggest that this RNA affects gp43-DNA interactions through global
effects on protein structure that occlude DNA-binding sites but leave
the enzyme accessible to interactions with the sliding clamp (RB69
gp45) and possibly other polymerase accessory proteins. We discuss the possible biological significance of putative RNA-binding motifs in the
N and palm domains of RB69 gp43.
*
This work was supported by NIGMS, National Institutes of
Health, Grant GM54627.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
§
Present address: Dept. of Genetics, Louisiana State University
Health Sciences Center, 533 Bolivar St., New Orleans, LA 70112.
¶
To whom correspondence should be addressed: Dept. of
Biochemistry SL 43, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA. Tel.: 504-584-1995; Fax: 504-584-1611; E-mail: karamoff@tulane.edu.
Copyright © 2002 by The American Society for Biochemistry and Molecular Biology, Inc.