Structural organization of transposable element mdg4 from Drosophila melanogaster and a nucleotide sequence of its long terminal repeats.

A mobile dispersed genetic element, mdg4 , approximately 7.5 kilobases (kb) long has been cloned from D. melanogaster genome. Chromosomal bands have only few sites of mdg4 , but it always hybridizes to the chromocenter. The location of mdg4 varies among D. melanogaster strains. Blot hybridization shows that, in contrast to other mdg elements, mdg4 sequences are rather heterogeneous. Only few copies are full-length. A strong amplification of mdg4 has occurred during the in vitro cultivation of cells involving only one mdg4 variant. Long terminal repeats (LTRs) and flanking sequences have been sequenced in two cloned copies of transposable element mdg4 . In both cloned copies of mdg4 , LTRs have an identical nucleotide sequence 479 bp long. The mdg4 is flanked by four-base-pair direct repeats, short mismatched palindromes being present at the ends of each LTR. The termini of the mdg4 body contain an oligopurine stretch and a region partially complementary to D. melanogaster tRNA-Lys. Thus, structural organization of mdg4 LTRs is similar to that of several other mdg elements and retroviral proviruses.

Molecular cloning of double-stranded cDNA from the eye lens of the frog Rana temporaria: construction of the cDNA clonotheque and identification of a clone containing the nucleotide sequences of the lambda-crystallin gene.

Poly(A)+ RNA from the lens of the frog Rana temporaria contains three components (1200 +/- 50, 1000 +/- 50, and 900 +/- 50 bp in size) and a more heterogeneous RNA species with a length of 650-750 nucleotides. This RNA was used as a template for the AMV reverse transcriptase and Escherichia coli DNA-polymerase I and the total cDNA obtained was cloned in the PstI site of the pBR322 plasmid vector. Recombinant plasmids corresponding to abundant poly(A)+ RNA classes contain cDNA inserts from less than or equal to 200 to 1200 nucleotides in length. Part of the library (clonotheque) was divided into classes differing in the presence of absence of the restriction sites for BamHI, EcoRI and HindIII restriction endonucleases. The clones belonging to each of the five classes were characterized by the hybridization-translation test. The translation product of mRNA hybridizing with the clone pRT(1)294 has an M4 of about 22 000 and is specifically precipitated by the antiserum to lambda-crystallins of Rana temporaria. The size of the cDNA present in pRT(1)294, equal to 580 +/- 20 bp, is sufficient for coding the greater part of the lambda-crystallin amino acid sequence. On the basis of these data, we conclude that the clone pRT(1)294 codes for one of the frog lambda-crystallins.

[Enzymatic synthesis and molecular cloning of the pigeon alpha-globin structural gene]. / Fermentativnyi sintez i molekuliarnoe klonirovanie strukturnogo gena al'fa-globina golubia.

Double-stranded DNA synthesized from the pigeon globin mRNA by the subsequent actions of avian myeloblastosis virus reverse transcriptase and E. coli DNA polymerase I was split with nuclease S1 and inserted into PstI site in the plasmid pBR322 by poly(dG) times poly(dC) homopolymer extension technique using terminal deoxynucleotidyl transferase. E. coli transformants have been shown to contain pigeon globin sequences by colony hybridization with pigeon globin [32P]cDNA. The inserted DNA fragment deleted from recombinant DNA by PstI treatment hybridizes with globin cDNA. The maximal length of the inserted fragment measured in agarose gel was found to be 550--560 base pairs. Inserted sequences subjected to analysis by hybridization with alpha- and beta-[32P]cDNA have been ascribed to the pigeon alpha globin chain. EcoRI, HindIII, BglII, SalI, BamHI, PstI restriction enzymes did not cleave the inserted DNA fragment. Pigeon DNA coding alpha-globin chain contains recognition sites for AluI, HindII and HaeIII restriction enzymes. Part of the recombinant clones remains resistant to ampicillin and therefore in some of these clones the globin gene could be expressed.