Biomedical subjects

J Rine

Publications and source records attributed to J Rine.

111 records · Page 7Linked to original sources

PubMed1980

The trans action of HMRa in mating type interconversion.

HML and HMR are the sites of cryptic mating type genes in the yeast Saccharomyces cerevisiae. In the presence of the HO gene, the information from HML or HMR (an a or alpha cassette) is transferred to the mating type locus (MAT). HML, HMR, and MAT are located on chromosome III, yet are widely separated. Similarly, in other yeasts, at least some of the genes involved in mating typing interconversion are linked to the mating type locus. We demonstrate here that a cassette donor (HMR) and the cassette target (MAT) need not be physically linked for successful mating type interconversion. In particular, we show that HMRa on one chromosome can donate an a cassette to the mating type locus on a homologous chromosome III.

Chromosome Mapping↗

PubMed1979

A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci.

A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S. cerevisiae. This suppressor, sir1-1, restores mating ability to mat alpha 1 and mat alpha 2 mutants and restores sporulation ability to mat alpha 2 and mata1 mutants. MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to alpha-factor, both properties of a/alpha diploids. Furthermore, sir1-1 allows MATa/MATa, mat alpha 1/mat alpha/, and MAT alpha/MAT alpha strains to sporulate efficiently. All actions of sir1-1 are recessive to SIR1. The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed. The ability of sir1-1 to suppress the mat alpha 1-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to alpha. Thus, as predicted by the cassette model, HMa is functionally equivalent to MAT alpha since it supplies functions of MAT alpha. We propose that sir1-1 is defective in a function. Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HM alpha.

Chromosome Mapping↗

PubMed1977

Facilitation at neuromuscular junctions: contribution to habituation and dishabituation of the Aplysia gill withdrawal reflex.

The gill withdrawal reflex of Aplysia has been used as a model for studying the neuronal mechanisms of habituation, a behavioral plasticity. We have assessed the contribution of neuromuscular facilitation, an elementary synaptic plasticity, during habituation of the reflex by recording gill muscle potentials, which we show are caused by excitatory junctional potentials. These potentials show systematic frequency-dependent changes in amplitude. The gill withdrawal evoked by central motor neuron firing during each habituation trial is determined by facilitation of the excitatory junctional potentials during the trial and the facilitated state of the initial excitatory junctional potential in a trial, determined by neuron activity prior to the trial. The neuromuscular junctions, therefore, act like a frequency-dependent amplifier of central motor activity. They are fully responsive to the dynamic changes of motor neuron firing that occurs during habituation and especially after dishabituation.

Action Potentials↗