mRNA 3′ End Formation by Vaccinia Virus: Mechanism of Action of a Heterodimeric Poly(A) Polymerase

Abstract

Historically, vaccinia viral enzymes have provided fundamental insights into general enzymological processes. Reasons for this include their amenity to genetic approaches, the relative ease with which they can be purified in adequate quantities, their genetic location within a relatively small, intronless, completely sequenced genome, and the recognizable sequence similarity often observed with corresponding cellular enzymes. Mechanisms by which the ubiquitous poly(A) tail is added to mRNA 3′ ends are not fully characterized in any organism. Concurrently with the characterization of the metazoan, yeast, andEscherichia colipoly(A) polymerases, some recent biochemical and crystallographic studies of the vaccinia enzyme have provided glimpses of how a heterodimeric poly(A) polymerase might elongate the poly(A) tail.