The six conserved helicase motifs of the UL5 gene product, a component of the herpes simplex virus type 1 helicase-primase, are essential for its function - PubMed (original) (raw)

The six conserved helicase motifs of the UL5 gene product, a component of the herpes simplex virus type 1 helicase-primase, are essential for its function

L A Zhu et al. J Virol. 1992 Jan.

Abstract

The UL5 protein of herpes simplex virus type 1, one component of the viral helicase-primase complex, contains six sequence motifs found in all members of a superfamily of DNA and RNA helicases. Although this superfamily contains more than 20 members ranging from bacteria to mammalian cells and their viruses, the importance of these motifs has not been addressed experimentally for any one of them. In this study, we have examined the functional significance of these six motifs for the UL5 protein through the introduction of site-specific mutations resulting in single amino acid substitutions of the most highly conserved residues within each motif. A transient replication complementation assay was used to test the effect of each mutation on the function of the UL5 protein in viral DNA replication. In this assay, a mutant UL5 protein expressed from an expression clone is used to complement a replication-deficient null mutant with a mutation in the UL5 gene for the amplification of herpes simplex virus origin-containing plasmids. Eight mutations in conserved regions and three similar mutations in nonconserved regions of the UL5 gene were analyzed, and the results indicate that all six conserved motifs are essential to the function of UL5 protein in viral DNA replication; on the other hand, mutations in nonconserved regions are tolerated. These data provide the first direct evidence for the importance of these conserved regions in any member of the superfamily of DNA and RNA helicases. In addition, three motif mutations were introduced into the viral genome, and the phenotypic analyses of these mutants are consistent with results from the transient replication complementation assay. The ability of these three mutant UL5 proteins to form specific interactions with other members of the helicase-primase complex, UL8 and UL52, indicates that the functional domains required for replication activity of UL5 are separable from domains responsible for protein-protein interactions. It is anticipated that this type of structure-function analysis will lead to the identification of protein domains that contribute not only to the enzymatic activities of helicase or primase but also to protein-protein interactions within members of the complex.

PubMed Disclaimer

Similar articles

Cited by

References

    1. Proc Natl Acad Sci U S A. 1986 Feb;83(4):907-11 - PubMed
    1. Nature. 1986 May 22-28;321(6068):439-41 - PubMed
    1. EMBO J. 1986 Aug;5(8):1939-44 - PubMed
    1. Mol Cell Biol. 1986 Apr;6(4):1218-27 - PubMed
    1. Proc Natl Acad Sci U S A. 1987 Jan;84(1):16-20 - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources