Radiation induction of the receptor tyrosine kinase gene Ptk-3 in normal rat astrocytes.
Radiation-induced gene expression was examined in rat astrocyte cultures using differential display of mRNA via reverse transcriptase-polymerase chain reaction. A 0.3-kb cDNA that was consistently observed in irradiated cultures but not in unirradiated cultures was cloned and sequenced. It was found to be identical to Ptk-3, a receptor tyrosine kinase gene identified recently. The protein encoded by Ptk-3 is a member of a novel class of receptor tyrosine kinases whose extracellular domain contains regions of homology with coagulation factors V and VIII and complement component C1. Northern blot analysis revealed that the expression of Ptk-3 was increased in rat astrocytes by 0.5 h after exposure to 10 Gy and remained at the same elevated level for at least 24 h. The maximum increase occurred after 5 Gy. Cloning studies indicated the presence of at least two Ptk-3 mRNA transcripts, which are probably the result of an alternative splicing mechanism. The short isoform lacks a 37-amino acid sequence in the glycine/proline-rich juxtamembrane region. The splicing pattern of the Ptk-3 gene was not altered by radiation. However, the ratios of the longer to the shorter mRNA transcripts differed between adult cortex, neonatal cortex and in vitro astrocyte cultures.
Sakuma
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S
Department of Experimental Radiotherapy, University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Saya
H
H
Ijichi
A
A
Tofilon
P J
PJ
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000201:enzymology / Q000528:radiation effects*; D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D000070819:Discoidin Domain Receptor 1; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; C511169:DDR1 protein, rat; D000070819:Discoidin Domain Receptor 1; D020794:Receptor Protein-Tyrosine Kinases