H-2-linked genetic control of the plaque-forming cell response to sheep red blood cells

The role of genes linked to the H-2 locus in effecting an immune response to SRBC was examined using strains of mice which differ in the classes of antibodies produced following multiple injections with SRBC. While H-2-linked gene action appeared to be at the level of regulating the number of plaque-forming cells (PFC) present in the spleens of different strains following two injections with SRBC, non-H-2-linked immune response genes seemed to determine whether an IgM-IgG switch occurred as well as how much of each antibody class was produced by the number of PFC available as a result of H-2-linked gene intervention. Mapping studies showed that the H-2-linked genetic effects were due to either the requirement for two genes or the presence of genes located between I-B and H-2D.     

Membrane excitability expressed in human neuroblastoma cell hybrids

The voltage-sensitive Na+ channel is responsible for the action potential of membrane electrical excitability in neuronal tissue. Three methods were used to demonstrate the presence of neurotoxin-responsive Na+ channels in two hybrid cell lines resulting from the fusion of excitable human neuroblastoma cells with mouse fibroblasts. Only one of the two electrically active hybrid cell lines maintained the sensitivity of the neuroblastoma parent to tetrodotoxin (TTX). The other hybrid, although electrically active, was not responsive to TTX or scorpion venom. Comparisons of the patterns of expression of membrane excitability and of chromosome complements in these human neuroblastoma cell hybrids suggest that the phenotype of membrane excitability is composed of genetically distinct elements.     

Context affects nuclear protein localization in Saccharomyces cerevisiae.

Proteins destined for the nucleus contain nuclear localization sequences, short stretches of amino acids responsible for targeting them to the nucleus. We show that the first 29 amino acids of GAL4, a yeast DNA-binding protein, function efficiently as a nuclear localization sequence when fused to normally cytoplasmic invertase, but not when fused to Escherichia coli beta-galactosidase. Moreover, the nuclear localization sequence from simian virus 40 T antigen functions better when fused to invertase than when fused to beta-galactosidase. A single amino acid change in the T-antigen nuclear localization sequence inhibits the nuclear localization of simian virus 40-invertase and simian virus 40-beta-galactosidase in Saccharomyces cerevisiae. From these results, we conclude that the relative ability of a nuclear localization sequence to act depends on the protein to which it is linked.     

A candidate gene family for the mouse t complex responder (Tcr) locus responsible for haploid effects on sperm function

The mouse t complex responder (Tcr) locus plays a central haploid-specific role in the transmission ratio distortion phenotype expressed during germ cell differentiation in t-carrying males. The accumulated data map Tcr to a region of less than 500 kb. Over 400 kb of this region has been cloned and consists entirely of sequences associated with a clustered family of large cross-hybridizing elements of 30 kb to 70 kb in size. We have characterized a gene family within this region that is expressed uniquely in male germ cells with a complex pattern of RNA processing. Antibodies produced against a product of the putative open reading frame recognize a testes-specific polypeptide. Genetic data support the hypothesis that this polypeptide(s) functions to effect the Tcr phenotype.     

Recombination sites in the HLA class II region are haplotype dependent

We have analyzed DNA sequence polymorphisms of DQ alpha and DQ beta chains from three haplotypes from the DRw52 family: DR5 DQw1 (FPA, GM3106), DRw6 DQw1 (CB6B, 10w9060), and DRw6 DQw3 (AMALA, 10w9064). The results indicate that the DR5 DQw1 and DRw6 DQw1 haplotypes have arisen by recombination between the DR beta 1 and DQ alpha loci. This contrasts with our previous analysis of DR4 DQ"Wa", DR3 DQ"Wa", and DR7 DQw3 haplotypes, all of which appear to have arisen by virtue of recombination between DQ alpha and DQ beta. Thus, there appear to be at least two different sites where recombination has occurred within the DR and DQ subregions. These differing patterns of recombination were interpreted in the context of the three major family groups of class II haplotypes, the DRw53, DRw52, and DR1/2 haplotype families. The data indicate that haplotypes from these family groups tend to undergo recombination at different locations. We propose that these differences in site of recombination are a reflection of differences in the molecular organization of the haplotypes belonging to each family group.     

A chimeric ubiquitin conjugating enzyme that combines the cell cycle properties of CDC34 (UBC3) and the DNA repair properties of RAD6 (UBC2): implications for the structure, function and evolution of the E2s.

The CDC34 (UBC3) protein from Saccharomyces cerevisiae has a 125 residue tail that contains a polyacidic region flanked on either side by sequences of mixed composition. We show that although a catalytic domain is essential for CDC34 activity, a major cell cycle determinant of this enzyme is found within a 74 residue segment of the tail that does not include the polyacidic stretch or downstream sequences. Transposition of the CDC34 tail onto the catalytic domain of a functionally unrelated E2 such as RAD6 (UBC2) results in a chimeric E2 that combines RAD6 and CDC34 activities within the same polypeptide. In addition to the tail, the cell cycle function exhibited by the chimera and CDC34 is probably dependent on a conserved region of the catalytic domain that is shared by both RAD6 and CDC34. Despite this similarity, the CDC34 catalytic domain cannot substitute for the DNA repair and growth functions of the RAD6 catalytic domain, indicating that although these domains are structurally related, sufficient differences exist to maintain their functional individuality. Expression of the CDC34 catalytic domain and tail as separate polypeptides are capable of only partial function; thus, while the tail displays autonomous structural characteristics, there is considerable advantage gained when both domains coexist within the same polypeptide. The ability of these and other derivatives to restore partial function to a cdc34 temperature-sensitive mutant but not to a disruption mutant suggests that interaction between two CDC34 polypeptides is a requirement of CDC34 activity. Based on this idea we propose a model that accounts for the initiating steps leading to multi-ubiquitin chain synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)