Heterogeneity of eel thyrotropin beta mRNAs is due to a minisatellite in the 3' untranslated region of the gene.
The aim of this study was to determine the causes of the high heterogeneity, in the number and the length, of the thyrotropin (TSH) beta mRNA in the European eel. Northern blot analysis showed that removal of the poly(A) tail did not affect this heterogeneity. PCR amplification on reverse-transcribed pituitary RNAs (RT) showed the main source of heterogeneity to be a highly variable region in the 3' untranslated region (UTR). PCR amplification of the 3' UTR from RTs and genomic DNAs demonstrated that the high variability reflected polymorphism within the eel TSH beta gene. Isolation and sequencing of 3' UTR amplification fragments showed that the variable region comprised more or less exact repetitions of a 26-42-bp fragment. The number of repetitions varied from one allele to another. This variable region could be characterized as a minisatellite. In conclusion, instability of a minisatellite in the 3' UTR of the TSH beta gene generated the multiple and widely differing TSH beta mRNAs.
Laboratoire de Physiologie Générale et Comparée, Muséum National d'Histoire Naturelle, URA CNRS 90, 7, rue Cuvier, 75231, Paris, cedex 05, France.
B
B
Pradet-Balade
C
C
Salmon
A
A
Hardy
B
B
Quérat
D000595:Amino Acid Sequence; D000811:Anguilla / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000097:blood / Q000302:isolation & purification; D018076:DNA, Complementary; D005260:Female; D015723:Gene Library; D014644:Genetic Variation; D007438:Introns; D018598:Minisatellite Repeats; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013972:Thyrotropin / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013972:Thyrotropin; D004247:DNA