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Biomedical subjects

Y Koltin

Publications and source records attributed to Y Koltin.

At least 55 records · Page 3Linked to original sources
PubMed1980

Assignment of functions to segments of the DsRNA genome of the Ustilago virus.

The genome of the 3 Ustilago maydis viruses, known to be associated with the "killer phenomenon", is segmented. The distribution of the viral functions on different segments has been partly resolved. The reported comparative study, of a series of mutants with deleted segments of the genome and of hybrid variants containing segments of the related viruses, provides additional information on the location of various functions and on the interrelations among the different segments. The data indicates that the functions related to the maintenance of the viral information are located on the H segments. Among these segments some function overlap exists. The maintenance of the M and L segments is dependent on the functions located on the H segments. The functions related to the killer phenotype are distributed on the M2 and L1 segments. These functions include the determination of the killer specificity. The H segments play no role in the determination of the killer specificity and the specificity is determined by the M2 segment. The L segment is essential for the expression of the killer phenotype but it is suggested that the information for the toxin resides in the M2 segment.

Basidiomycota↗
PubMed1980

The killer phenomenon in Ustilago: electron microscopy of the dsRNA encapsidated in individual virus particles.

From earlier studies with the Ustilago maydis virus and other dsRNA viruses it is known that discrete dsRNA segments typical of each virus are obtained by extraction. A variation exists with respect to the encapsidation of these segments among different viruses. The encapsidation of the genome in individual particles of the Ustilago virus was examined by electron microscopy after disruption of virus particles. The study included the P6 wild-type and 2 mutants containing only part of the genome. The results indicate that most virus particles of the wild-type and the mutants contain up to 12-14 X 10(6) daltons of dsRNA. Since the largest extracted molecule is 3.2 X 10(6) D these findings suggest that an individual particle may contain more than one segment of dsRNA. Free linear molecules that exceed in size the extracted segments were also found following the disruption of each of the 3 virus types examined. Thus, the viral genome seen segmented after extraction is organized as a concatamer in the capsid and each virus particle can contain an entire viral genome consisting of each type of the segments seen after extraction, a repeat of a single segment or a random assortment. In each case the information may be organized as a concatamer.

Basidiomycota↗
PubMed1979

Nuclease activity associated with the Ustilago maydis virus induced killer proteins.

An in vitro nuclease activity was found to be associated with the purified killer proteins of Ustilago maydis. The proteins are effective against single stranded RNA, single and double stranded DNA. Endonucleolytic activity was confirmed by cleavage of circular molecules of 0x174 and PM2. Double stranded RNA did not appear to serve as a substrate.

Basidiomycota↗
PubMed1979

Mutational analysis of natural alleles in and affecting the B incompatibility factor of Schizophyllum.

Primary mutations in the alleles of alpha 1 and beta 7 of the B incompatibility factor of Schizophyllum were induced with X rays. An additional mutation unlinked to the B factor and affecting its regulatory function was detected. This mutation is effective in monokaryons with most B-factor specificities. The spectra of induced mutations in different alleles is discussed in reference to a polarity in the expression of the recognition function and the regulatory function by each locus of the B incompatibility factor.

Agaricales↗
PubMed1978

Repair of UV-induced damage in wild-type and mutant strains of Schizophyllum commune.

The basidiomycete fungus Schizophyllum commune was found to have both photo-repair and dark-repair systems for UV-induced damage. Three UV-sensitive mutants were isolated and characterized for ability to repair UV-induced damage in light and dark, and for cross-sensitivity to caffeine and methyl methanesulfonate. Two of the mutants were damaged, to different extents, in their capacity for excision repair; one of these mutants was also probably damaged in post-replication repair. The third mutant was damaged only in post-replication repair.

Caffeine↗
PubMed1977

Virus-like particles in Ustilago maydis: mutants with partial genomes.

Mutants with partial genomes for the virus-like particles of U. maydis were recovered following treatment with nitrosoguanidine. Examination of the properties retained by progeny of genetic crosses indicates that the 2.9 X 10(6) dalton component of double-stranded RNA contains the information for capsid formation and dsRNA replication. Other components appear to contain the information for killer function and immunity to killer. The use of such mutants for studies on the evolution of viruses with segmented genomes is discussed.

Basidiomycota↗
PubMed1976

Inheritance of killer phenotypes and double-stranded RNA in Ustilago maydis.

Three different killer specificities in U. maydis are inherited cytoplasmically and transmitted by cell fusion. Each killer generates low frequencies of specifically immune forms in crosses with sensitive strains. The properties of immunity to each killer are also inherited cytoplasmically and transmitted by cell fusion. Killer strains carry virus-like particles about 41 nm in diameter. Each killer possesses distinct double-stranded RNA components that range in molecular weight from 0.46 X 10(6) to 2.9 X 10(6). Two components are shared by all three killers. Immune strains possess new forms. Crosses and heterokaryons between different killers revealed unilateral or mutual restrictions that prevent inclusion of two killer specificities in the same cell.

Basidiomycota↗
PubMed1976

Suppression of the killer phenotype in Ustilago maydis.

Nineteen sensitive cell lines of U. maydis were crossed with three killer strains and sample progenies were screened for killer segregation patterns. Crosses involving 11 lines gave killer frequencies ranging from 71%-100% of the progeny and 4:0 segregations in tetrads. Segregations in some crosses involving each of the remaining 8 lines gave killer frequencies from 0%-58% and mixed tetrads containing both non-killer and killer meiotic products. Many of the killers were unstable on further culture. Killer suppression showed varying degrees of specificity, appeared to be cytoplasmically determined for at least one strain, and was associated with possession of dsRNA in this strain and one other. No dsRNA was detected in two other suppressive strains. There was no evidence for segregation of nuclear maintainer genes for any of the killer determinants.

Basidiomycota↗