Trends in Endocrinology & Metabolism
Isoform/variant mRNAs for sex steroid hormone receptors in humans
Section snippets
Structure of the gene encoding ERα
In addition to coding exons 1–8 4, 5, eight untranslated 5′-exons in the upstream region of exon 1 6, 7, 8, 9, 10, 11, 12, and an ‘intronic’ exon S located between exons 3 and 4 [13] are identified in the gene encoding human ERα (Fig. 1).
Isoform/variant mRNAs encoding ERα
In mRNA encoding human ERα, type 2, 3, 4 and 6 isoform/variant transcripts have been reported. In addition, the ‘type 7-like’ mRNA variant of ERα that is generated by a point mutation in the intron located between exons 5 and 6 is also discussed.
Type 2: Since
Structure of the gene encoding ERβ
The coding region of the gene encoding human ERβ comprises exons 1–7 28, 29 and five alternative exon 8s 30, 31, 32. In addition, seven untranslated 5′-exons in the upstream region of exon 1 32, 33, and an ‘intronic’ exon M between exons 4 and 5 [34] have been identified (Fig. 2).
Isoform/variant mRNAs encoding ERβ
In mRNA encoding human ERβ, types 2, 4, 5 and 6 isoform/variant transcripts have been reported. The type 7 isoform mRNA reported in mRNA encoding rodent ERβ is also discussed here 35, 36, 37. It has been reported that
Structure of the gene encoding PR
The coding region of the gene encoding human PR comprises exons 1–8 45, 46, 47. In addition, ‘intronic’ exons have also been identified: exons T [48] and S [49] between exons 3 and 4; and exons i45a [50] and i45b [50] between exons 4 and 5 (Fig. 3).
Isoform/variant mRNAs encoding PR
In mRNA encoding the human PR, isoform/variant transcript types 1, 2, 6 and 7 have been identified.
Type 1: By using upstream transcription start sites and downstream ones, PR isoform B and A mRNAs are generated. The longer PR isoform B mRNA and the
Structure of the gene encoding AR
The open reading frame of the gene encoding human AR comprises exons 1–8 59, 60, 61 (Fig. 4). Unlike the other genes encoding human SSHRs, no reports on 5′-untranslated exons, ‘intronic’ exons or alternative coding exons of the gene encoding human AR are currently available.
Isoform/variant mRNAs encoding AR
In mRNA encoding the human AR, only type 1 and type 2 isoform/variant transcripts have been identified. Many variant mRNAs are generated in humans, especially in cases of androgen insensitivity syndrome 62, 63; however, most
Conclusions
Human cDNAs encoding SSHRs, ERα [4], PR [45] and AR 59, 60 were cloned in the mid-1980s, and the genomic organization of the coding regions of these genes was clarified by the late 1980s 5, 47, 61. There have since been several landmark studies of isoform/variant mRNAs encoding SSHRs. First, an untranslated exon was identified in the gene encoding human ERα 6, 7, 8, 9, 10, 11, 12, and thereafter, various untranslated 5′-exons were recognized in the genes encoding ERα and ERβ. Second,
Acknowledgements
The authors thank Dr Selma M Soyal for providing the information on the genomic location of the PR exons T and S. This work was supported by grant No. 08671879, and No. 11671605 to SH from the Japanese Ministry of Education.
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