The 5' noncoding and flanking regions of the avian very low density apolipoprotein II and serum albumin genes. Homologies with the egg white protein genes.
1983; Elsevier BV; Volume: 258; Issue: 7 Linguagem: Inglês
10.1016/s0021-9258(18)32659-0
ISSN1083-351X
AutoresRobert J.G. Haché, R Wiskocil, Monika Vasa, Rabindra Roy, Peter C. K. Lau, R G Deeley,
Tópico(s)Molecular Biology Techniques and Applications
ResumoWe have isolated and sequenced the 5' proximal exons and flanking regions of the chicken very low density apolipoprotein II (apo-VLDLII) and serum albumin genes.These genes specify the most abundant mRNA species present in livers of hens or estrogen-treated roosters.Sequencing revealed that the promoter region of the estrogen-dependent apo-VLDLII gene contained at least two potential transcriptional initiation sites, preceded by appropriately positioned "ATA" sequences.One is homologous with the cap site of the ovalbumin gene, and the other exhibits a match of 10 out of 12 nucleotides with the cap site of the serum albumin gene.S1 nuclease mapping indicates that both sites are active in uiuo, although the "ovalbumin"-like site is by far the most efficient at all stages of the estrogenic response.The relative efficiencies of these two sites are maintained during in vitro transcription of truncated templates.A third site, that was not anticipated from sequencing data, is active in uiuo but inactive in vitro.A conserved 5' flanking element, initially identified during studies on egg white protein genes, is also present upstream from the apo-VLDLII and serum albumin genes.Its removal does not affect initiation site selection in uitro.Regions of the apo-VLDLII and ovalbumin genes extending 100 nucleotides downstream from the "TATA box" contain several striking homologies that suggest a common mode of evolution.Previous studies on the fine structure of estrogen-responsive genes have focused primarily on genes specifying major chicken egg white proteins (1-4).The 5' flanking regions of these genes have been sequenced and putative regulatory sites have been identified, both on the basis of structural comparison and more recently by direct hormone receptor-binding studies (5, 6).At the moment they are the only estrogenresponsive genes that have been characterized at this level.We have recently isolated the apo-VLDLII' gene and approximately 20 kb of flanking sequences (7).Apo-VLDLII is a major constituent of the very low density lipoprotein fraction of hen serum.It is a small phospholipid-binding protein (8), synthesized in the liver and ultimately deposited in the developing oocyte, where it forms part of the low density fraction of the yolk (9-11).Expression of the apo-VLDLII gene is
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