Mark J Churcher

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The binding site for tat protein on TAR RNA has been defined in quantitative terms using an extensive series of mutations. The relative dissociation constants for the mutant TAR RNAs were measured using a dual-label competition filter binding assay in which 35S-labelled wild-type TAR RNA (K1) was competed against 3H-labelled mutant TAR RNA (K2). The error(More)
Stimulation of transcriptional elongation by the human immunodeficiency virus type 1 Tat protein is mediated by CDK9, a kinase that phosphorylates the RNA polymerase II carboxyl-terminal domain (CTD). In order to obtain direct evidence that this phosphorylation event can alter RNA polymerase processivity, we prepared transcription elongation complexes that(More)
SBDS protein (deficient in the inherited leukemia-predisposition disorder Shwachman-Diamond syndrome) and the GTPase EFL1 (an EF-G homolog) activate nascent 60S ribosomal subunits for translation by catalyzing eviction of the antiassociation factor eIF6 from nascent 60S ribosomal subunits. However, the mechanism is completely unknown. Here, we present(More)
The human immunodeficiency virus type 1 (HIV-1) Tat protein activates transcription elongation by stimulating the Tat-activated kinase (TAK/p-TEFb), a protein kinase composed of CDK9 and its cyclin partner, cyclin T1. CDK9 is able to hyperphosphorylate the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase during elongation. In addition(More)
A monoclonal antibody was raised against the major capsid protein L1 of human papillomavirus type 16, using a recombinant vaccinia virus that expresses the L1 protein, as a target for screening. This antibody, designated CAMVIR-1, reacted with a 56 kilodalton protein in cells infected with L1-vaccinia virus, and the protein was present in a predominantly(More)
The effects of mutations in human immunodeficiency virus type-1 (HIV-1) long terminal repeat on initiation and on Tat-mediated trans-activation were studied using cell-free transcription assays. All the elements that are necessary for efficient transcription initiation in vitro are included in the core promoter. This region contains three tandem Sp1 binding(More)
The human immunodeficiency virus type 1 transactivator protein, tat, specifically stimulates transcription from the viral long terminal repeat. We used cell-free transcription systems to test whether tat can stimulate transcriptional read-through of an artificial terminator sequence (e.g., a stable RNA stem-loop structure followed by a tract of nine uridine(More)
The acyclovir-resistant mutant SC16 R9C2 (H.J. Field, G. Darby, and P. Wildy , J. Gen. Virol. 49:115-124, 1980) has been shown to contain two resistance loci which segregate independently on recombination with wild-type virus. One locus is in thymidine kinase, and the other is in DNA polymerase. Both induced enzymes have altered properties, thymidine kinase(More)
Different isolates of human immunodeficiency virus type 1 (HIV-1) vary in the cell tropisms they display, i.e., the range of cell types in which they are able to establish a productive infection. Here, we report on the phenotypes of recombinants between two molecularly cloned strains of HIV-1. Our results prove that the envelope glycoprotein gp120 is solely(More)
The HIV-1 trans-activator protein, Tat, is a potent activator of transcriptional elongation. Tat is recruited to the elongating RNA polymerase during its transit through the trans-activation response region (TAR) because of its ability to bind directly to TAR RNA expressed on the nascent RNA chain. We have shown that transcription complexes that have(More)