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The nucleotide sequence of the rpoB gene of Salmonella typhimurium has been determined in this work. It was compared with known sequences of the gene from other sources and the conservative regions were detected. This allowed some interesting conclusions to be made about the distribution of the functional domains in bacterial RNA polymerase and about the three-dimensional structure of its p subunit.DNA-dependent synthesis of all types of RNA in bacteria is catalyzed by RNA polymerase, an oligomeric enzyme with the subunit structure .$j?'o (for review see [l]). To study the structure and the mechanism of RNA polymerase action, amino acid sequences of all subunits of the E. coli enzyme were determined [2-51, the subunit in contact with the DNA template, RNA product and substrates were identified [6] and several mutations leading to RNA polymerase resistance to the antibiotics rifampicin and streptolydigin were localized [7 -101. These investigations indicated an important role for the RNA polymerase p subunit at all stages of RNA synthesis. This paper presents the results of cloning and sequencing of the rpoB gene coding for the subunit of Salmonella typhimurium RNA polymerase.The primary structure of the Salmonella typhimurium rpoB gene coding for RNA polymerase p subunit was determined (4.2 kb in toto). On comparison with homologous Escherichia coli and tobacco chloroplasts gene sequences, nine conservative and six variable regions of the [ j subunit structure were identified. Analysis of available genetic data allowed some preliminary conclusions to be made concerning the location of the putative functional domains in the structure of the p subunit of bacterial RNA polymerase and to devise a hypothesis about the spatial proximity of the central part of the p subunit to its N-and C-terminal domains.

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Human endogenous retroviruses (HERVs), probably representing footprints of ancient germ‐cell retroviral infections, occupy about 1% of the human genome. HERVs can influence genome regulation through expression of retroviral genes, either via genomic rearrangements following HERV integrations or through the involvement of HERV LTRs in the regulation of gene expression. Some HERVs emerged in the genome over 30 MYr ago, while others have appeared rather recently, at about the time of hominid and ape lineages divergence. HERVs might have conferred antiviral resistance on early human ancestors, thus helping them to survive. Furthermore, newly integrated HERVs could have changed the pattern of gene expression and therefore played a significant role in the evolution and divergence of Hominoidea superfamily. Comparative analysis of HERVs, HERV LTRs, neighboring genes, and their regulatory interplay in the human and ape genomes will help us to understand the possible impact of HERVs on evolution and genome regulation in the primates. BioEssays 22:161–171, 2000. ©2000 John Wiley & Sons, Inc.