A human gene encoding diazepam-binding inhibitor/acy1-CoA-binding protein: transcription and hormonal regulation in the androgen-sensitive human prostatic adenocarcinoma cell line LNCaP.
Diazepam-binding inhibitor (DBI)/acyl-CoA-binding protein (ACBP) is a highly conserved 10-kD polypeptide expressed in various organs and implicated in the regulation of multiple biological processes such as GABAA/benzodiazepine receptor modulation, acyl-CoA metabolism, steroidogenesis, and insulin secretion. To extend our knowledge about the biology of DBI/ACBP and to elucidate the molecular mechanisms responsible for regulating DBI/ACBP gene expression, we have studied the androgen-regulated expression of DBI/ACBP transcripts in the human prostatic adenocarcinoma cell line LNCaP and have cloned and characterized a human gene encoding DBI/ACBP. Northern blotting, reverse transcription-assisted polymerase chain reaction (RT-PCR), ribonuclease protection, and 5' RACE analysis (rapid amplification of cDNA ends) of DBI/ACBP transcripts in LNCaP cells revealed androgen-regulated expression of multiple transcripts originating from multiple transcription start sites and alternative processing. The most abundant type of transcripts (referred to as type 1 transcripts) encodes genuine DBI/ACBP of 86 amino acids, while the minor type (type 2 transcripts) harbors an insertion of 86 bases and might encode an unrelated protein of 67 amino acids. Examination of a cloned DBI/ACBP gene revealed a structural organization of four exons present in all transcripts and one alternatively used exon present only in type 2 transcripts. The promoter region is located in a CpG island and lacks a canonical TATA box. Transient transfection of DBI/ACBP promoter fragments into LNCaP cells demonstrated that a region of 1.1 kb upstream of the translation start site is able to drive high-level expression of luciferase in LNCaP cells in an androgen-regulated fashion. Taken together these data indicate that the isolated human gene encoding DBI/ACBP is functional, has a high degree of structural similarity with the corresponding rat gene, exhibits hallmarks of a typical housekeeping gene, and harbors cis-acting elements that are at least partially responsible for androgen-regulated transcription in LNCaP cells.
Swinnen
J V
JV
Laboratory for Experimental Medicine and Endocrinology, Faculty of Medicine, Onderwijs en Navorsing, Gasthuisberg, Catholic University of Leuven, Belgium.
Esquenet
M
M
Rosseels
J
J
Claessens
F
F
Rombauts
W
W
Heyns
W
W
Verhoeven
G
G
D000230:Adenocarcinoma / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D026261:Diazepam Binding Inhibitor; D015972:Gene Expression Regulation, Neoplastic; D005796:Genes; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011471:Prostatic Neoplasms / Q000235:genetics*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D002352:Carrier Proteins; D017931:DNA Primers; D026261:Diazepam Binding Inhibitor