Structural features of the herpes simplex virus alpha gene 4, 0, and 27 promoter-regulatory sequences which confer alpha regulation on chimeric thymidine kinase genes

Abstract

Previous studies have shown that herpes simplex virus genes form three groups, alpha, beta, and gamma, whose expression is coordinately regulated and sequentially ordered in a cascade fashion. Chimeric genes constructed by fusion of the coding and 5' nontranslated leader sequences of the thymidine kinase (TK) gene to the sequences upstream from the site of initiation of transcription of alpha genes 4 and 27 are regulated as alpha genes and are induced in cells converted to TK+ phenotype by infection with TK- virus. In alpha gene 4 (S. Mackem and B. Roizman, Proc. Natl. Acad. Sci. U.S.A. 79:4917-4921, 1982), both the promoter and the regulatory region are separable and movable. The promoter permits expression but not induction when fused to TK in the noncoding leader region of the gene. The regulator, when fused to the promoter of an expressible but noninducible portion of the natural beta TK, renders the gene inducible as an alpha gene; it consists of multiple regulatory units acting cumulatively. In this paper, we report on the precise site of initiation of transcription of alpha gene 0 within the inverted b sequences of the L component of viral DNA. We also report the following. (i) The chimeric gene consisting of the coding and 5' nontranslated leader regions of the TK gene fused to portions of the domain of alpha gene 0 extending largely upstream from the site of initiation of transcription of alpha gene 0 was regulated in the same fashion as the alpha 4- and alpha 27-TK chimeras. The regulatory region in the alpha gene 0 is largely upstream from nucleotide - 140. (ii) The promoter-regulatory regions of alpha genes 0, 4, and 27 share TATA sequences, A + T-rich (consensus) sequences occurring in regulating regions of alpha genes 0 and 4 in more than one copy, and multiple G + C-rich inverted repeats. The relation of these sequences to the function of the promoter-regulatory regions of the alpha genes is discussed.