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The sequence of Lyt-2 cDNA shows that it is a new member of the immunoglobulin super gene family. Analysis of the predicted amino acid sequence indicates that the Lyt-2 polypeptide is synthesized with a 27-amino acid leader, and that the mature protein has an immunoglobulin variable region (Ig V)-related sequence of 100 amino acids, an extracellular spacer of 43, a transmembrane region of 38, and an intracytoplasmic region of 27 amino acids. Lyt-2 and its human analogue Leu-2 are 56% homologous; analysis indicates that the Ig V-related domains of the two molecules have evolved away from each other faster than the carboxyl-terminal half of the proteins.

We have shown previously that transfection of mouse L-cells with DNA from JM, a human T-cell line expressing certain T-cell differentiation antigens, yields stable transfectants expressing one or another of these antigens. The identities of the antigens were confirmed by immunoprecipitation and SDS-polyacrylamide gel electrophoresis. We now report that our procedure--co-transfection with the chicken thymidine kinase gene (tk) and whole cellular DNA, selection with hypoxanthine-aminopterin-thymidine (HAT), and staining of the cells with fluorochrome-conjugated monoclonal antibodies and fluorescence-activated cell-sorter (FACS) selection--yields transfectants expressing a variety of cell-surface molecules (19 of 21 investigated), most at a frequency of about one per 10(3) Tk+ transformants. Of these, 9 of 12 were transferred and expressed as readily using DNA from cells which did not express the cell-surface antigens as from tissues or cells that did express them.

We show that mRNAs for alpha 2(I), alpha 1(III), and alpha 2(V) collagens are regulated by estradiol in the immature rat uterus. Clones for alpha 2(I) and alpha 1(III) collagen were induced in a cDNA library prepared from estradiol-stimulated rat uterine mRNA. Alpha 2(I) collagen cDNA was identified by its characteristic hybridization pattern on Northern blots and hybridization to known probes. The sequence of alpha 1(III) collagen cDNA showed 91% amino acid sequence homology with the corresponding 525-nucleotide segment of human alpha 1(III) procollagen cDNA. Type I and type III collagen mRNAs were coordinately regulated, and showed peaks of induction at 4 and 24 hr. Three injections of estradiol, 24 hr apart, produced induction maxima 24 hr apart. The third induction, however, was suppressed relative to the first, suggesting that estrogen-stimulated factors may act to negatively regulate the uterine response to estrogen.

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