Changes in the relative abundance of type I and type II lck mRNA transcripts suggest differential promoter usage during T-cell development.
The lck gene, which encodes the lymphoid cell-specific tyrosine protein kinase p56lck, is expressed from two widely separated promoters. The proximal promoter gives rise to a type I lck transcript, and the distal promoter gives rise to a type II transcript. We found that the ratio of the two transcripts changed during T-cell maturation. Type I lck mRNA was twofold more abundant than the type II transcript in early fetal thymocytes. In the adult, the type I and type II lck mRNAs were present in approximately equal amounts in immature thymocytes expressing the heat-stable antigen. In contrast, there was five- to ninefold more type II lck than type I lck mRNA in more mature thymocytes that did not express the heat-stable antigen and in splenic T cells. This change in relative transcript abundance probably reflects activation of the distal promoter and inactivation of the proximal promoter during T-cell maturation in the thymus. It is possible that the two promoters are regulated by different trans-acting factors whose expression is regulated during T-cell maturation.
Reynolds
P J
PJ
Salk Institute, San Diego, California 92138-9216.
Lesley
J
J
Trotter
J
J
Schulte
R
R
Hyman
R
R
Sefton
B M
BM
D000818:Animals; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens; D002454:Cell Differentiation; D005333:Fetus; D005796:Genes; D051379:Mice; D008806:Mice, Inbred AKR; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D013154:Spleen / Q000201:enzymology / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D013950:Thymus Gland / Q000201:enzymology; D014158:Transcription, Genetic
D000945:Antigens, Differentiation, T-Lymphocyte; D015704:CD4 Antigens; D016827:CD8 Antigens; D012333:RNA, Messenger; D011505:Protein-Tyrosine Kinases