Characterization of mRNA transcripts and organization of human SP-A1 and SP-A2 genes.
In the present study, we have characterized the mRNA transcripts and intron-exon organization of the human surfactant protein (SP)A1 and SP-A2 genes. By primer extension analysis of mRNA isolated from human fetal lung explants using an oligonucleotide primer to exon II (as delineated in the SP-A1 gene), a minimum of nine primer extended transcripts was observed. Rapid amplification of cDNA ends was used to amplify the primer extended transcripts for sequence analysis. Sequence analysis of 47 full-length primer extended cDNAs and comparison with the sequences of the genes encoding SP-A1 and SP-A2 revealed four different classes of transcripts of the SP-A2 gene and five different classes of transcripts of the gene encoding SP-A1. A major difference between SP-A2 and SP-A1 mRNA transcripts is that SP-A2 transcripts are always comprised of sequences contained within six exons; the extra exon in SP-A2 (exon II of VI) encodes additional 5'-untranslated sequence and is located between exons I and II of SP-A1. By contrast, the majority of transcripts of the SP-A1 gene are comprised of sequences contained within five exons. In the cases of both SP-A1 and SP-A2 genes, a small proportion of the mRNA transcripts contain sequences present in alternate exons. In addition, the majority of the SP-A1 mRNA transcripts are initiated 5 bp downstream of the transcription initiation site of SP-A2. In our companion paper [McCormick and Mendelson. Am. J. Physiol. 266 (Lung Cell. Mol. Physiol. 10): L367-L374, 1994], we report that the SP-A1 and SP-A2 genes are differentially regulated during development and by adenosine 3',5'-cyclic monophosphate and glucocorticoids in human fetal lung in culture.
McCormick
S M
SM
Department of Biochemistry, Cecil H. and Ida Green Center for Reproductive Biology Sciences, University of Texas Southwestern Medical Center, Dallas 75235-9038.
Boggaram
V
V
Mendelson
C R
CR
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons; D005796:Genes; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D011110:Polymorphism, Genetic; D011510:Proteolipids / Q000235:genetics*; D037662:Pulmonary Surfactant-Associated Protein A / Q000031:analogs & derivatives*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000235:genetics*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic
D018076:DNA, Complementary; D015345:Oligonucleotide Probes; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012333:RNA, Messenger; C445842:SFTPA1 protein, human; C445843:SFTPA2 protein, human