Molecular cloning of a novel luteinizing‐hormone/ human‐chorionic‐gonadotropin‐receptor cDNA

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Abstract
The biological action of luteinizing hormone/human chorionic gonadotropin (lutropin/choriogonadotropin) in the ovary is mediated by interaction with its specific receptor. Lutropin/choriogonadotropin‐receptor hnRNA is processed into multiple mRNAs. However, nucleotide sequences for many of the transcripts, including the major form (6.7 kb), have yet to be determined. In an attempt to identify a cDNA encoding the major transcript, we have isolated a 3.5‐kb cDNA clone from a rat ovary cDNA library. The 3.5‐kb cDNA recognized only two (6.7 kb, 4.4 kb) of the three (6.7, 4.4, 2.6 kb) ovarian lutropin/choriogonadotropin‐receptor transcripts when used as a probe. The first 732 nucleotides of the newly identified 3.5‐kb cDNA showed 98% identity to the 3′ untranslated region (3′ UTR) of the previously cloned cDNA corresponding to the 4.4‐kb transcript. Southern blot analysis indicated that the 3.5‐kb cDNA and the C‐terminal domain of the lutropin/choriogonadotro‐pin‐receptor originate from the same gene. Oligonucleotide‐directed cleavage of the 6.7‐kb lutropin/ choriogonadotropin‐receptor mRNA by RNase H revealed that the newly identified 3.5‐kb cDNA is a 3′ extension of the 4.4‐kb transcript. We propose that the nucleotide sequence of the 6.7‐kb lutropin/choriogonadotropin‐receptor transcript, the major form found in rat ovary, contains a long 3′ UTR, which has not been previously identified.