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B T White

Publications and source records attributed to B T White.

7 recordsLinked to original sources
PubMed1994

Mutants of Neurospora crassa that alter gene expression and conidia development.

Several genes have been identified that are highly expressed during conidiation. Inactivation of these genes has no observable phenotypic effect. Transcripts of two such genes, con-6 and con-10, are normally absent from vegetative mycelia. To identify regulatory genes that affect con-6 and/or con-10 expression, strains were prepared in which the regulatory regions for these genes were fused to a gene conferring hygromycin resistance. Mutants were then selected that were resistant to the drug during mycelial growth. Mutations in several of the isolates had trans effects; they activated transcription of the corresponding intact gene and, in most isolates, one or more of the other con genes. Most interestingly, resistant mutants were obtained that were defective at different stages of conidiation. One mutant conidiated under conditions that do not permit conidiation in wild type.

Cinnamates↗
PubMed1993

Structural characterization and expression analysis of the Neurospora conidiation gene con-6.

The gene con-6 of Neurospora crassa is expressed during the formation of asexual spores (conidia), but it is not expressed in mycelium. con-6 mRNA appears upon induction of conidiation and reaches high levels at the late stages of conidiation, and in mature conidia. The CON6 polypeptide and a CON6-beta-Gal fusion protein were present at high levels only in free conidia. Shortly after spore germination con-6 mRNA disappears and the CON6 polypeptide is degraded. CON6 is a small, hydrophilic polypeptide containing a repeat sequence; it not homologous to any known protein but has features resembling the late embryogenesis abundant proteins of maize. Inactivation of con-6 by the repeat-induced point mutation process had no demonstrable effect on formation or germination of conidia. Upstream sequence comparisons for con-6 and other con genes identified a common potential regulatory sequence, designated CRS-B. DNA mobility shift analyses with cell extracts identified a factor that bound to synthetic DNA fragments containing this sequence. This binding factor was present in mycelium but not in conidiating cultures. Experiments with independent integrated con-6'-'lacZ translational fusions revealed substantial variability of expression among transformants carrying identical fusion constructs: This variability may be due to the differential methylation of transformant DNA noted by others.

Amino Acid Sequence↗
PubMed1991

Further characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus: nucleotide sequence analysis.

Conditional lethal amber nonsense mutants of vesicular stomatitis virus, Indiana serotype, classified in complementation group I (the L gene), synthesize truncated versions of the L protein. This paper reports further characterization of mutants AmbL1, AmbL2 and AmbL3 by nucleic acid sequence analysis, which was achieved by sequencing L mRNA directly using appropriate synthetic oligonucleotides. In each case a single point mutation altered a glutamine-specifying codon to an amber stop codon. The L mRNA from wild-type and revertant viruses was sequenced for comparison. Of the revertants sequenced, each had reverted by back mutation within the same codon as the original mutation. A revertant of AmbL2 reverted by a second site mutation, also within the same codon as the original mutation. These mutants may be useful for assigning functions to different parts of the L polypeptide chain.

Base Sequence↗
PubMed1987

Movement of myosin fragments in vitro: domains involved in force production.

We have used the Nitella-based movement assay to localize the site of force production in myosin. Methods were developed to use nonfilamentous myosin or proteolytic fragments of myosin in place of the thick filaments used in the original assay. In the experiments described here, the tail of myosin or its subfragments is anchored via antibodies to the surface of small particles. Nonfilamentous myosin or its subfragments move along Nitella actin cables at speeds similar to those obtained with filamentous myosin. We generated short HMM, a myosin fragment containing the heads and only 400 A of the tail. Although short HMM lacks the "hinge" region proposed by Harrington to be the site of force generation, and is incapable of forming thick filaments, it moves along actin at speeds above 1 micron/sec. Therefore, neither a thick filament nor the carboxy-terminal 1100 A of the tail is required for movement along actin. The results indicate that force production occurs in or near the myosin heads.

Actins↗
PubMed1987

Isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus.

We describe the isolation and characterization of conditional lethal amber nonsense mutants of vesicular stomatitis virus (VSV), Indiana serotype. The mutants were isolated from a chemically mutagenized stock of wild-type virus by their ability to grow on genetically engineered cells which express a Xenopus laevis amber suppressor tyrosine tRNA gene (su+ cells) but not on the non-suppressor parental cells (su- cells). Five mutations were assigned to complementation group I (the L gene) and one to complementation group V (the G gene) by complementation analysis using temperature-sensitive mutants representing each of the five VSV cistrons. Four of the group I mutants were observed to synthesize a novel polypeptide species in su+ cells. Immunoprecipitation and immunoblotting studies using monospecific antisera directed against the N and C termini of the VSV L protein showed that the novel polypeptide species contain N terminal- but not C terminal-specific sequences and can thus be considered to be truncated versions of the L protein. In addition a protein which again contained N terminal- but not C terminal-specific sequences could be identified for the fifth group I mutant. Revertants of four of the group I mutants were isolated on the su- cells. The revertants all synthesized normal L protein but not the putative truncated version.

DNA Mutational Analysis↗