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Biomedical subjects

R J Watson

Publications and source records attributed to R J Watson.

115 records · Page 7Linked to original sources
PubMedDate not supplied

Regulation of the cell cycle by B-Myb.

B-Myb is a cell-cycle-regulated member of the Myb transcription factor and, like c-Myb, has been implicated in regulation of hematopoietic cell proliferation and differentiation. In this study we have examined the mechanisms by which B-Myb regulates the cell cycle. We found that the ability of B-Myb both to promote Saos-2 cells into the S phase of the cell cycle and to overcome G1 arrest mediated by overexpression of the retinoblastoma-related p107 protein was correlated with the capacity of B-Myb to form an in vivo complex with p107, but was independent of its transactivation function. Further experiments using a B-Myb dominant-negative protein suggested that transcriptional activation of genes regulated through Myb DNA-binding sequences was required for cell proliferation. Our experiments suggest, therefore, that B-Myb influences cell cycle progression at two distinct levels: by inhibiting p107 and by inducing transcription of specific target genes.

Cell Cycle↗
PubMedDate not supplied

Respiratory mechanics in the open chest: effects of parietal pleurae.

To understand how the parietal pleurae affect the mechanical behavior of the human respiratory system after the chest wall is opened by median sternotomy, we studied 18 anesthetized/paralyzed patients immediately before coronary artery bypass grafting surgery. Elastances and resistances of the total respiratory system (ETr, Rrs) were calculated from measurements of airway pressure and flow during mechanical ventilation in the frequency and tidal volume ranges of normal breathing. Elastances and resistances of the lungs (EL, RL), chest wall (Ecw, Rcw) were also estimated from measurements of esophageal pressure. Data were collected in the closed chest, after median sternotomy with the parietal pleurae intact and after the left parietal pleura was opened for internal mammary artery harvest. After sternotomy with pleurae intact (n = 14), Ers did not change but Rrs decreased (p < 0.05). Ecw (including the contribution of the pleurae) was higher than in the closed chest (p < 0.05) while EL and RL were lower (p < 0.05); Rcw did not change. Opening the left pleura (n = 10) decreased Ers (p < 0.05), but Rrs did not change. We conclude that the chest wall/pleurae compartment offers significant impedance to lung expansion after sternotomy and rib retraction, unless one pleura is opened.

Adult↗
PubMedDate not supplied

Characterization and nucleotide sequence of a colicin-release gene in the hic region of plasmid ColE3-CA38.

Downstream from its colicin and immunity genes (col. imm), Escherichia coli plasmid ColE3-CA38 contains a 0.81-kb DNA segment, the hic region, which is required for high colicin production. Characterization of derived plasmids, carrying the col-imm operon but varying in the hic region, showed that the latter functions in lacuna production, colicin release, cell death, and lysis. The hic gene expression after induction was shown to be dependent on the col gene promoter. The nucleotide sequence of the 0.81-kb region was determined and the hic gene localized to its imm-distal portion following an open reading frame (ORF) with no known function. There are two overlapping ORFs in that portion of the sequence, one of which was identified as the hic gene by its partial homology to lysis gene H of CloDF13. The 3' half of the hic gene is non-essential and contains a terminator-like DNA sequence. Preceding the gene, there are also inverted repeats which may attenuate its transcription.

Amino Acid Sequence↗
PubMedDate not supplied

Analysis of the C4-dicarboxylate transport genes of Rhizobium meliloti: nucleotide sequence and deduced products of dctA, dctB, and dctD.

Rhizobium meliloti transports succinate, fumarate, malate, and aspartate by means of the dicarboxylate transport system, which is encoded by dct genes located on the exo megaplasmid. Analysis of these genes using Tn5 insertion mutagenesis revealed three complementation groups within a 5.9-kb HindIII fragment. The sequence of this fragment and the sites of Tn5 insertion were determined. Three genes, dctA, dctB, and dctD, were identified as the only three open-reading frames in locations consistent with the complementation data. The dctA gene is preceded by the sequence CTGGCACG-N4-TTGCT, which is characteristic of promoters requiring the ntrA-encoded protein for activation. The dctA-encoded protein is highly hydrophobic and contains eight potential transmembrane helices, indicating that it is probably the structural component of the transport system responsible for movement of dicarboxylates from the periplasm across the inner membrane. The dctB and dctD genes are transcribed in the opposite direction to dctA. They encode proteins with homology to the R. leguminosarum bv. viceae dicarboxylate transport proteins regulating expression of dctA and to other proteins comprising two-component regulatory systems. The dctB-encoded protein includes a putative periplasmic N-terminal domain that senses the presence of dicarboxylates and a C-terminal cytoplasmic domain that activates the dctD-encoded protein. The C-terminus of the dctD-encoded protein shows homology to several DNA-binding proteins, indicating that it is probably the domain which binds DNA in the dctA promoter region to regulate dctA transcription. All the R. meliloti mutants altered in dctA, dctB, and dctD were complemented by the dct region from R. l. bv. viceae.

Amino Acid Sequence↗