SEQUENCE OF A CDNA-ENCODING THE BETA-4-SUBUNIT OF MURINE INTEGRIN

A cDNA coding for the beta4 Subunit of murine integrin (mbeta4) has be en cloned and sequenced using mRNA from a murine lung carcinoma as the template. The 5' sequence contains two AUG codons, the second of whic h initiates synthesis of the mature protein. The cDNA sequence has an open reading frame coding for 1748 amino acids (aa), including a signa l peptide, cysteine-rich region, serine- and threonine-rich region, tr ansmembrane domain, and a cytoplasmic domain of over 1000 aa. Overall, the deduced Mbeta4 aa sequence has 88% identity with the human beta4 subunit (hbeta4) sequence deduced from the sequence of placental mRNA. Reverse transcriptase-polymerase chain reaction using primers flankin g splice sites for two variant forms of hbeta4 transcripts provided ev idence for alternate splicing of RNA in the murine spleen and to a les ser extent in the skin, uterus, and thymus but was found at only one o f the two alternative sites. Five potential glycosylation sites presen t in the extracellular domain of hbeta4 are conserved in Mbeta4. One t yrosine in the terminal region of the cytoplasmic domain (position 160 0) is conserved between Mbeta4 and hbeta4 and has the consensus sequen ce for tyrosine phosphorylation. Finally, a genomic restriction map of mbeta4 shows that the gene is about 40 kb in length. No restriction-f ragment length polymorphisms were detected between BALB/c liver and BA LB/c lung carcinoma DNA.