Differential expression of the human insulin-like growth factor II gene. Characterization of the IGF-II mRNAs and an mRNA encoding a putative IGF-II-associated protein.
Insulin-like growth factor II (IGF-II) is a polypeptide of 67 amino acids which is thought to play an important role in fetal growth and development. The human IGF-II gene is situated on chromosome 11, very close to the insulin gene. It extends over 30 kb of chromosomal DNA and consists of five noncoding exons (exons 1-4 and 4B) followed by three protein encoding exons (exons 5-7), one of which (exon 7) contains a long 3'-untranslated region. Here we show that differential initiation of transcription can occur at three distinct promoter sites, resulting in the appearance of mRNA species of different lengths. These promoters show a tissue-specific and a development-specific regulation of expression. Furthermore, we have determined the entire nucleotide sequence of the 3'-terminal exon, exon 7, which is about 4 kb long and contains 3.8 kb of 3'-untranslated sequences. This completes the elucidation of the human IGF-II gene structure. Surprisingly, Northern blot analysis of fetal and adult RNA with a probe derived from the 3'-nontranslated region of exon 7 detects a novel 1.8 kb mRNA which appears to be coordinately expressed with the IGF-II mRNAs. In vitro translation of this 1.8 kb mRNA results in the formation of a translation product of 8.3 kDa, which compares well with the size of a predicted translation product from a 252-nucleotides-long open reading frame.
de Pagter-Holthuizen
P
P
Laboratory for Physiological Chemistry, State University of Utrecht, The Netherlands.
Jansen
M
M
van der Kammen
R A
RA
van Schaik
F M
FM
Sussenbach
J S
JS
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D005091:Exons; D005796:Genes; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics*; D013002:Somatomedins / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II; D004247:DNA