Bovine steroid 21-hydroxylase: regulation of biosynthesis

Abstract

A recombinant cDNA clone, PBC21-1, specific for bovine steroid 21-hydroxylase cytochrome P-450 (P-450C21) was identified in a bovine adrenocortical cDNA library, and this identity was confirmed by nucleotide sequencing which revealed significant amino acid homology (77%) with human P-450C21 cDNA. The pBC21-1 insert is 1.7 kilobases in length and includes a 1128 base pair region that encodes the C-terminal 376 amino acids of bovine P-450C21 as well as 535 base pairs of 3'-untranslated sequence. A novel feature of this insert is a 20 base pair intervening sequence near the 5' end, apparently the result of an aberrant splicing event. Northern blot analysis reveals that bovine P-450C21 is encoded by two transcripts, 2.3 and 2.0 kilobases in length which are detected in adrenal cortical RNA. Bovine liver, heart, kidney, and corpus luteum do not contain detectable P-450C21 transcripts. Regulation of P-450C21 gene expression by adrenocorticotropin was investigated with pBC21-1 and bovine adrenocortical cells in primary, monolayer culture. Treatment with ACTH or analogues of cAMP increases the steady-state levels of P-450C21 RNA in such cell cultures. In vitro transcription run-on assays suggest that this increase is, at least in part, due to the enhanced transcriptional activity of the P-450C21 gene.

Interrenal steroid 21-hydroxylase in eels: primary structure, progesterone-specific activity and enhanced expression by ACTH

“…In this study, infusion of ACTH increased both plasma cortisol levels and interrenal expression of the P450c21 gene in eels. This suggests that the increase in plasma cortisol level is mediated, at least in part, by the increased expression of P450c21 gene as already observed in mammals (John et al 1986, Provencher et al 1992. In addition, other enzymes responsible for corticosteroid synthesis may also be activated by ACTH as reported in rats (LeHoux et al 1998).…”

“…The similarity of P450c21 protein between eels and mammals was low (41-44%). Nevertheless, the putative functional domains for steroid binding, heme binding and proton transfer, as identified in mammalian P450c21s (John et al 1986, Crawford et al 1992, White & Speiser 2000, displayed high identity (74-100%) between eels and mammals, suggesting their importance for enzyme activity.…”

“…In the present study, P450c21 mRNA was expressed exclusively in the anterior quarter (P1) of the head kidney, suggesting that the interrenal steroidogenic cells are represented only in this part. The expression of P450c21 mRNA has also been detected exclusively in the adrenal cortex in mammals (John et al 1986, Zhou et al 1997. On the other hand, other eel proteins related to corticosteroidogenesis such as P450c17 and P450c11 and StAR are expressed in the gonads and/or interrenal (Jiang et al 1998, Kazeto et al 2000.…”

Structure of human steroid 21-hydroxylase genes.

“…A corrected sequence of a longer bovine cDNA clone has been obtained (33) and is about 70% homologous to the human amino acid A Taq I site is present in the 3'-untranslated region of the cDNA 200 bp upstream of the polyadenylylation site; the remainder of the genomic sequence was obtained using a primer complementary to the 3' end of the mRNA. This 200-bp region is sufficiently short that hybridization of the cDNA clone to genomic DNA is weak under stringent hybridization conditions.…”

Transcriptional activation of adrenocortical steroidogenic genes by high potassium or low sodium intake

“…hydroxysteroid dehydrogenase [18]; pBCZI_I, containing a partiallength insert coding for bovine P450,*, [19]; and pl lp-OHase-I .2, which contains a 1.2-kb cDNA insert cloned from a mouse Y 1 cDNA library that contains P450,,, sequences from the 5'-untranslated region to + 1153 [20]. This cDNA recognizes 1 l/I-hydroxylase and aldosterone synthase mRNAs [21].…”