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M Meselson

Publications and source records attributed to M Meselson.

6 recordsLinked to original sources
PubMed1979

Studies of cloned sequences from four Drosophila heat shock loci.

DNA cloned from the D. melanogaster (Oregon R) heat shock loci at 63BC and 95D codes for the 83,000 and the 68,000 dalton heat shock proteins, respectively. Both coding sequences occur once per haploid genome. Sequences complementary to messenger RNA for the 70,000 dalton heat shock protein are represented five times, twice at 87A and three times at 87 C. The copies at 87A differ characteristically from those at 87C in an interval of a few hundred bp near the 5' end of the messenger sequence, and the corresponding two classes of hsp 70 messenger RNA are found on polysomes after heat shock. Within this differential region, there is about 15% divergence between messenger sequences cloned from the two loci, while in the rest of the messenger region examined the homology is much closer although still imperfect. Unexpectedly, considerable homology is found between the sequence for the 68,000 dalton heat shock protein at 95D and the sequences for the 70,000 dalton protein at 87A and 87C, and between these sequences and a site in 87D. Messenger RNA molecules of 2.4, 2.55 and 3.05 kb code for the 68,000, 70,000 and 83,000 dalton heat shock proteins and hybridize to apparently uninterrupted DNA sequences of 2.1, 2.25 and 2.6 kb, respectively.

Animals↗
PubMed1978

Sequence organization and transcription at two heat shock loci in Drosophila.

The heat shock loci of Drosophila melanogaster chromosome subdivisions 87A and 87C have been studied by using cloned DNA. Both sites contain a number of copies of a 2,4-kilobase (kb) region homologous to mRNA for the 70,000-dalton heat shock protein. In situ hybridization to chromosomal RNA shows that transcripts of this sequence accumulate at both sites after temperature elevation. At 87C there is a 1.5-kb repeated sequence homologous to another heat shock RNA. One cloned segment includes two to three tandem copies of this sequence located 0.8 kb from the beginning of a 2.4-kb message region. RNA complementary to the 1.5-kb repeat acccumulates at 87C after temperature elevation, but does not code for any known heat shock protein. In the sibling species D. simulans, there are sequences located and transcribed at 87A and 87C that are homologous to the melanogaster 2.4-kb message sequence. The 1.5-kb repeat, however, is absent from 87C in simulans and no heat shock RNA homologous to it can be detected.

Animals↗
PubMed1977

Transcription at two heat shock loci in Drosophila.

Transcription at two heat shock loci in Drosophila melanogaster, in subdivisions 87A and 57C, was investigated by hybridization in situ with 3H-labeled messenger, nuclear RNA and whole cell RNA from cells cultured at elevated temperature. What appears to be the same 9 x 10(5) dalton heat shock message hybridizes at both sites. At 87a, little additional hybridization is obtained with nuclear or whole cell RNA. In contrast, at 87C the saturation level of hybridization by nuclear and whole cell RNA is much higher than that obtained with the message alone. This evidence for extensive hybridization at 87C but not at 87A by RNA distinct from the message is confirmed by the finding that excess nonradioactive message competes away most of the hybridization by 3H-labeled nuclear and whole cell RNA at the latter locus but not at the former. The noncompetable RNA migrates on an electrophoretic gel as a heterogeneous population of molecules, extending to sizes both larger and smaller than the message. These and other observations lead to the conclusion that a 87A transcription includes little more than sequences complementary to the 9 x 10(5) dalton message, while at 87C, there are sequences complementary to the same message and extensive additional sequences complementary to other species of RNA.

Base Sequence↗
PubMed1975

Localization of RNA from heat-induced polysomes at puff sites in Drosophila melanogaster.

Heat treatment of D. melanogaster tissue culture cells causes drastic changes in the pattern of protein synthesis and the size distribution of polysomes. Like the heat shock puffs on polytene chromosomes which appear while preexisting puffs regress, heat shock proteins appear on gels while the synthesis of preexisting proteins is sharply reduced, and heat-induced polysomes appear on gradients after preexisting polysomes have disappeared. Most of the poly(adenylic acid)-containing RNA isolated from high-temperature polysomes sediments in sucrose gradients and migrates in gels as a rather narrow band. This RNA is of sufficient size to code for one particular protein that is found to account for more than half of the total synthesis at high temperature. The RNA hybridizes in situ mainly at chromosome sub-division 87B, the site of the major heat shock puff.

Adenine Nucleotides↗