Operators and promoters in the OR region of phage 434

The OR operator region of phage 434 contains three 14 bp blocks with sequence ACAAGA-A--TTGT which are presumed to be the 434 repressor recognition sites. Operator constitutive mutations are located in two of these blocks, while a mutation affecting repressor levels in the lysogenic state is located in the third. Two transcripts obtained in vitro, one leftwards and one rightwards, are tentatively identified as the Prm and PR transcription starts. the arrangement of the 434 operator region appears to be very similar to that of the OR of phage lambda.

Characterization of a mouse DNA clone containing an immunoglobulin variable region gene

A 4.8 kilobase mouse embryo DNA fragment was inserted into a phage lambda genome and was subsequently characterized by electron microscopy, restriction enzyme mapping and partial DNA sequencing. This fragment contains a 400 base sequence which is homologous to that of an immunoglobulin light lambda chain mRNA which spans 3.3 to 3.7 kilobases from one end of the fragment. Restriction enzyme mapping as well as partial nucleotide sequencing of the 3' terminal of the homology region confirm the previous conclusion [Tonegawa, Brack, Hozumi and Schuller, Proc. Natl. Acad. Sci. USA. 74, 3518-3522 (1977)] that the cloned DNA fragment contains a Vlambda gene sequence which is separate from any Clambda sequence.

Transcription of cloned tRNA gene fragments and subfragments injected into the oocyte nucleus of Xenopus laevis

Cloned 3.18 kilobase fragments of Xenopus laevis DNA containing genes for tRNAMet1 and for at least one other 4S RNA species are transcribed rapidly after their injection into the nucleus of X. laevis oocytes. The newly synthesized RNA can be resolved by gel electrophoresis into a few predominant 4S RNA species and a series of slower migrating components. One of the 4S RNA species appears to be identical, by fingerprint analysis, to the tRNAMet1 isolated by hybridization of somatic cell RNA to this cloned tRNA gene fragment (tDNA). Thus, the tRNAMet1 produced after injection can be both fully processed and modified. Its rate of synthesis is estimated to be about 6 x 10(9) molecules/hr in each oocyte injected with 2 ng of tDNA. When the tDNA fragment is cleaved into two halves with restriction endonuclease Sst I, each injected half gives rise to a subset of the RNAs produced after injection of the intact fragment. This experiment thus suggests the presence of at least two transcriptional units on this cloned tDNA. This simple way of biologically testing defined restriction fragments may be of value for analyzing the functional organization of other cloned eukaryotic DNA units.

The 5S genes of Drosophila melanogaster

We have cloned embryonic Drosophila DNA using the poly (dA-DT) connector method (Lobban and Kaiser, 1973) and the ampicillin-resistant plasmid pSF2124 (So, Gill and Falkow, 1975) as a cloning vehicle. Two clones, containing hybrid plasmids with sequences complementary to a 5S RNA probe isolated from Drosophila tissue culture cells, were identified by the Grunstein and Hogness (1975) colony hybridization procedure. One hybrid plasmid has a Drosophila insert which is comprised solely of tandem repeats of the 5S gene plus spacer sequences. The other plasmid contains an insert which has about 20 tandem 5S repeat units plus an additional 4 kilobases of adjacent sequences. The size of the 5S repeat unit was determined by gel electrophoresis and was found to be approximately 375 base pairs. We present a restriction map of both plasmids, and a detailed map of of the5S repeat unit. The 5S repat unit shows slight length and sequence heterogeneity. We present evidence suggesting that the 5S genes in Drosophila melanogaster may be arranged in a single continuous cluster.

A simple, general procedure for purifying restriction endonucleases

A simple, general method for purifying restriction endonucleases is described. The method employs precipitation of nucleic acids from crude extracts with polyethyleneimine followed by affinity chromatography on columns of heparin covalently linked to agarose. Most of the sixteen enzymes tested could be purified to a degree sufficient for DNA sequencing work by this method sometimes supplemented by at most one step of ion exchange chromatography.

Lambda repressor regulates the switch between PR and Prm promoters

The DNA region containing the Or operator, Pr and Prm promoters and their transcription initiations is sequenced. By binding to Or, repressor turns off Pr, turns on Prm and at higher concentrations turns off Prm, regulating its own synthesis. Prm mRNA is unique in beginning immediately with the initiation of translation, without a preceding leader sequence.

Two restriction endonucleases from Bacillus globiggi

The sites of action of the restriction enzyme Bgl II on lambda DNA are mapped. This enzyme recognises the sequence 5' ...AGATCT...3' and makes staggered cuts producing sticky ends. In lambda DNA, the second A in this sequence is methylated about 50% of the time by a bacterial methylase absent in E. coli dam. In contrast to Bgl II, Bgl I makes many cuts in lambda DNA and produces 5' terminals which are not substrates for polynucleotide kinase.

Sequence of the OR operator of phage lambda

A sequence of 79 nucleotides from the lambda OR operator is obtained by primed transcription of repressor protected DNA fragments. The sequence contains the primary repressor binding site plus partial duplications which can be interpreted as secondary repressor binding sites.

Sequence of the PR promoter of phage lambda

The RNA polymerase binding site from the lambda PR promoter was isolated and sequenced. This DNA fragment contains the transcription initiation site and shares 25 nucleotides with OR. The sequence preceding the initiation site suggests that the promoter recognition site is not identical with the tight binding and initiation site.