Abstract
We have identified a cDNA whose sequence is preferentially expressed when quiescent fibroblasts are stimulated to proliferate. The steady-state levels of the mRNA corresponding to this clone, called 2A9, are increased by serum, platelet-derived growth factor, and epidermal growth factor, but not by insulin or platelet-poor plasma. mRNA levels of 2A9 are also increased in human acute myeloid leukemia. The 2A9 cDNA has been molecularly cloned from an Okayama-Berg library, and its complete nucleotide sequence has been determined. It has an open reading frame of 270 nucleotides, which has a 55% homology with the coding sequence of the beta-subunit of the S-100 protein, a calcium-binding protein that belongs (like calmodulin and the vitamin D-dependent intestinal calcium-binding protein) to the family of calcium-modulated proteins and is found in abundance in several human tumors, including melanoma. The S-100 protein and the deduced aminoacid sequence of 2A9 are also partially homologous to the small subunit of a protein complex that serves as a cellular substrate to tyrosine kinase. The partial homology of 2A9 (whose RNA is inducible by growth factors and is overexpressed in human acute myeloid leukemias) to the S-100 protein, other calcium-modulated proteins, and the subunit of a substrate for tyrosine kinase, is particularly interesting in view of the role attributed to calcium and tyrosine kinases in the regulation of cell proliferation.
Highlights
Molecular Cloningof the cDNA for a Growth Factor-inducible Gene with Strong Homology to 5-100,a Calcium-binding Protein*
We have identified a cDNA whose sequenceis pref- call calcium-modulatedproteins and which include calmoduerentially expressedwhenquiescentfibroblasts are lin [8].The homology between 2A9 and the &subunit of S
Fivehundred thousand recombinants strate for tyrosine kinase, is interesting of the Okayama-Berglibrary derived from SV40-transformedhuman in view of the role attributed to calcium andtyrosine fibroblasts [5], were screened at high density according to the procekinases in the regulation ocfell proliferation
Summary
BamHI insert derived from in the BamHI site of the Biotec (Madison, WI). An by growthfactorsand is overexpressed inhumanacute RNA probe of high specificactivity (4 X 10ecpm/gg) complementary myeloidleukemias) to the 5-100 protein,other cal- to the 82-bpBamHI insertwas synthesizedaccordingto the procedure cium-modulatedproteins,andthesubunit of a sub- described by Melton et al [14]. Fivehundred thousand recombinants strate for tyrosine kinase, is interesting of the Okayama-Berglibrary derived from SV40-transformedhuman in view of the role attributed to calcium andtyrosine fibroblasts [5], were screened at high density according to the procekinases in the regulation ocfell proliferation. Nine cDNA clones were isolated after secondary and tertiary screening, and six of them with the longest inserts were grownin large scale for. One of the five cDNA clones, called 2A9, was found to be overexpressed inhuman acute myeloid leukemias [2,3]
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