Orientation-dependent influence of an intergenic enhancer on the promoter activity of the divergently transcribed mouse Shsp/alpha B-crystallin and Mkbp/HspB2 genes.
The mouse Shsp/alphaB-crystallin and Mkbp/HspB2 genes are closely linked and divergently transcribed. In this study, we have analyzed the contribution of the intergenic enhancer to Shsp/alphaB-crystallin and Mkbp/HspB2 promoter activity using dual-reporter vectors in transient transfection and transgenic mouse experiments. Deletion of the enhancer reduced Shsp/alphaB-crystallin promoter activity by 30- and 93-fold and Mkbp/HspB2 promoter activity by 6- and 10-fold in transiently transfected mouse lens alpha-TN4 and myoblast C2C12 cells, respectively. Surprisingly, inversion of the enhancer reduced Shsp/alphaB-crystallin promoter activity by 17-fold, but did not affect Mkbp/HspB2 promoter activity in the transfected cells. In contrast, enhancer activity was orientation-independent in combination with a heterologous promoter in transfected cells. Transgenic mouse experiments established the orientation dependence and Shsp/alphaB-crystallin promoter preference of the intergenic enhancer in its native context. The orientation dependence and preferential effect of the Shsp/alphaB-crystallin enhancer on the Shsp/alphaB-crystallin promoter provide an example of adaptive changes in gene regulation accompanying the functional diversification of duplicated genes during evolution.
Swamynathan
Shivalingappa K
SK
Laboratory of Molecular and Developmental Biology, NEI/National Institutes of Health, Bldg. 6 Rm. 201, 6 Center Drive, Bethesda, MD 20892, USA.
Piatigorsky
Joram
J
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D017353:Gene Deletion; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D005822:Genetic Vectors; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012313:RNA / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000235:genetics* / Q000378:metabolism; D014018:Tissue Distribution; D014158:Transcription, Genetic; D014162:Transfection; D038203:alpha-Crystallin B Chain / Q000235:genetics* / Q000378:metabolism
D002352:Carrier Proteins; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C486699:Hspb2 protein, mouse; D011994:Recombinant Proteins; D015843:Serpins; D038203:alpha-Crystallin B Chain; C051324:kallistatin; D012313:RNA; D004247:DNA; D008156:Luciferases