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K L Calame

Publications and source records attributed to K L Calame.

25 records · Page 2Linked to original sources
PubMed1986

Binding in vitro of multiple cellular proteins to immunoglobulin heavy-chain enhancer DNA.

Seven protein-binding sites on the immunoglobulin heavy-chain (IgH) enhancer element have been identified by exonuclease III protection and gel retardation assays. It appears that the seven sites bind a minimum of four separate proteins. Three of these proteins also bind to other enhancers or promoters, but one protein seems to recognize exclusively IgH enhancer sequences. A complex of four binding sites, recognized by different proteins, is located within one 80-base-pair region of IgH enhancer DNA. Close juxtaposition of enhancer proteins may allow protein-protein interactions or be part of a mechanism for modulating enhancer protein activity. All IgH enhancer-binding proteins identified in this study were found in extracts from nonlymphoid as well as lymphoid cells. These data provide the first direct evidence that multiple proteins bind to enhancer elements and that while some of these proteins recognize common elements of many enhancers, others have more limited specificities.

Animals↗
PubMed1986

Alternative inducers of the rat metallothionein I gene cause distinct changes in chromatin structure in the 5' region of the gene.

We examined the chromatin structure of the rat metallothionein I gene, both in uninduced cells and in cells induced by heavy metals or dexamethasone, using hypersensitivity to DNase I as an assay. The metallothionein I gene of the H4IIE rat hepatoma cell line, expressed at basal level, has a single DNase I-hypersensitive site. This site maps between putative hormone and basal level control sequences. Induction of the gene by cadmium or zinc resulted in the appearance of a new hypersensitive site near the start site of transcription, in a region near the metal-regulatory elements. In contrast, induction of the metallothionein I gene by dexamethasone did not alter the basal pattern of hypersensitivity. Thus, different mechanisms of induction of metallothionein transcription lead to distinct alterations in the chromatin containing the 5' sequences regulating the expression of this gene.

Animals↗
PubMed1985

Immunoglobulin JH, C mu, and C gamma gene rearrangements in human B lymphocytes clonally transformed by Epstein-Barr virus.

Somatic rearrangements and deletions of immunoglobulin gene segments have been demonstrated in several types of murine B cells. In addition, rearrangements of the JH, C mu, and light chain immunoglobulin gene segments have been reported in human pre-B-cell leukemias and B-cell lymphomas. We have used recombinant DNA probes for the human JH, C mu, and C gamma immunoglobulin gene loci to analyze the genetic events associated with heavy chain gene expression in human B cells clonally transformed by Epstein-Barr virus. Southern hybridization analysis of BamHI-digested cell clone DNAs shows that these human B-cell clones often have bi-allelic JH rearrangements and that heavy chain isotype switching is associated with bichromosomal C mu and C gamma gene rearrangements. Deletions of germ line C mu and C gamma segments were observed that were sometimes bi-allelic. Overall, the observed rearrangements and deletions of heavy chain constant region genes suggest that human heavy chain class switching proceeds in a general order consistent with the proposed order of the heavy chain gene classes along chromosome 14.

B-Lymphocytes↗
PubMed1979

Location of an ampicillin resistance transposon, Tn1701, in a group of small, nontransferring plasmids.

By restriction endonuclease cleavage mapping and electron microscopic examination of heteroduplexes, we have identified an ampicillin resistance determinant transposon, designated Tn1701, in a group of small, nontransferring plasmids which confer resistance to ampicillin (Ap), sulfonamide (Su), and streptomycin (Sm). Plasmid NTP1, which mediates Ap resistance, contains Tn1701. Recombinant plasmids NTP3 (Ap Su) and NTP4 (Ap Su Sm) contain Tn1701, indicating that they were derived by transposition of Tn1701 from NTP1 to an unrelated plasmid, NTP2 (Su Sm). The transposon Tn1701 is very similar to the known ampicillin resistance transposons Tn1, Tn2, and Tn3 in its size (3.2 x 10(6) daltons), base sequence homology observed by heteroduplex formation, restriction endonuclease cleavage sites, and possession of a short inverted repeat sequence at both ends. Like the other TnA elements, Tn1701 also specifies a type TEM beta-lactamase.

Ampicillin↗