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L Gopalakrishnan

Publications and source records attributed to L Gopalakrishnan.

7 recordsLinked to original sources
PubMed1996

Cytochrome c oxidase subunit VIIa liver isoform. Characterization and identification of promoter elements in the bovine gene.

Cytochrome c oxidase subunit VIIa is specified by two nuclear genes, one (COX7AH) producing a heart/muscle-specific isoform and the other (COX7AL) a form expressed in all tissues. We have isolated both genes to examine their transcriptional regulation. Here, we characterize the core promoter of COX7AL and show that a 92-base pair region flanking the 5'-end promotes most of the activity of this gene. The 92-bp basal promoter contains sites for the nuclear respiratory factors NRF-1 and NRF-2, which have been shown to contribute to the transcription of a number of nuclear genes involved in mitochondrial respiratory activity, and also at least four Sp1 motifs. We show that both the NRF-1 and NRF-2 binding sites are functional in COX7AL and present evidence suggesting that interaction between the NRF-1 site and an upstream element contributes to expression.

Animals↗
PubMed1995

Structure, expression, and chromosomal assignment of the human gene encoding nuclear respiratory factor 1.

Nuclear respiratory factor 1 (NRF-1) is a transcription factor that acts on nuclear genes encoding respiratory subunits and components of the mitochondrial transcription and replication machinery. Here we describe the isolation and characterization of the human gene encoding NRF-1. The human genomic sequences detected with NRF-1 cDNA probes at high stringency are all contained within seven overlapping recombinant lambda clones. The NRF-1 gene encompassed by these recombinants spans approximately 65 kilobases (kb) and has 11 exons and 10 introns that range in size from 0.8 to 15 kb. A rapid amplification of cDNA ends-polymerase chain reaction product containing the 5'-terminus of the NRF-1 cDNA has two exons from the 5'-untranslated region and terminates at a major transcription initiation site identified by S1 nuclease mapping. A genomic fragment containing a portion of the 5'-terminal exon and an additional 1 kb upstream had a functional promoter that was active in transfected COS cells, HeLa cells, and L6 myoblasts. The transcription initiation site utilized by the transfected promoter corresponded to that used by the endogenous gene in vivo. NRF-1 mRNA was expressed at very low levels in rat tissues compared with cytochrome c and, unlike cytochrome c, was most abundantly expressed in lung and testis. The NRF-1 gene was localized to human chromosome 7 by analysis of DNA from a panel of human-hamster cell hybrids with human-specific NRF-1 polymerase chain reaction primers. This assignment was further refined to 7q31 by cohybridization of NRF-1- and chromosome 7-specific probes to human metaphase chromosomes. These analyses should be useful in evaluating the potential role of NRF-1 in mitochondrial diseases resulting from defects in the nuclear control of mitochondrial function.

Animals↗
PubMed1994

Differential regulation of respiratory chain subunits by a CREB-dependent signal transduction pathway. Role of cyclic AMP in cytochrome c and COXIV gene expression.

In vertebrate organisms, the molecular mechanisms by which extracellular signals regulate mitochondrial function and biogenesis are largely unknown. We have previously identified multiple cis-acting elements in both cytochrome c and cytochrome oxidase subunit IV (COXIV) genes that are likely targets for the regulated expression of respiratory chain components. We now demonstrate that cytochrome c but not COXIV mRNA is induced by cAMP through a mechanism involving transcriptional activation. Maximal induction occurs within 3 h and does not require de novo protein synthesis. The differential response of these genes is mediated by two distinct cAMP response elements (CREs) in the cytochrome c promoter region. Both elements function independently to drive cAMP-dependent expression from a heterologous promoter and within the proper cytochrome c promoter context. In addition, the binding properties of both elements to nuclear factors were characterized by competition DNase I footprinting, methylation interference footprinting, site-directed mutagenesis, and UV-induced DNA-protein cross-linking. The results are all consistent with the specific recognition of both CREs by CRE binding protein (CREB). A highly purified preparation of recombinant CREB formed a specific complex with each of the cytochrome c CREs identical to that formed with a crude nuclear fraction. In addition, the trans-activation of cytochrome c gene expression by recombinant CREB and protein kinase A in transfected cells was completely dependent on functional CREs within the promoter. These results establish that respiratory chain gene expression can be regulated directly by cAMP through a CREB-dependent signal transduction pathway.

Animals↗
PubMedDate not supplied

Girdlestone arthroplasty.

A series of 92 patient who underwent excision arthroplasty of the hip (Girdlestone arthroplasty) as a primary procedure is presented. The operation was performed for various conditions which included femoral neck fracture, rheumatoid arthritis, ankylosing spondylitis, tuberculosis, septic arthritis, unreduced posterior dislocation of long duration, fracture of the acetabulum, avascular necrosis of femoral head and bony ankylosis. Excision of head and neck of the femur was found to be an excellent salvage procedure for infected hips especially yielding uniformly satisfactory results at all ages irrespective of the disease. It provided a painless, mobile hip. Except for shortening and unstable gait, no other handicap was observed; the disadvantages of this handicap were outweighed by its advantages, compared with the disadvantages of other sophisticated hip operations such as replacement, and mould arthroplasties or even total hip replacement. Our results were excellent in 21% of cases, good in 44% and fair in 26% while they were poor in 9%. In view of its functional end results, we feel that this measure can be a good alternative to more modern and sophisticated hip operations in the form of partial or total hip replacement under Indian conditions.

Adolescent↗