Abstract
Utilizing a method called "differential display of mRNAs by means of polymerase chain reaction", the cDNA fragment of a thyroid hormone-responsive gene ZAKI-4 was cloned from cultured human skin fibroblasts. Northern blot analysis revealed that there were two ZAKI-4 mRNA species (3.4 and 1.4 kilobases (kb)), and they were up-regulated by a physiological concentration of triiodothyronine (T3). This T3 effect was abolished by the treatment with cycloheximide, indicating the possibility that gene ZAKI-4 is regulated by T3 in an indirect fashion, through an intermediate product of T3, rather directly by T3 itself. No effect of T3 on ZAKI-4 mRNA stability suggested that T3 induces the mRNA at the transcriptional level. Rapid amplification of cDNA ends confirmed the presence of two mRNA species. ZAKI-4 mRNA was detected in heart, brain, liver, and skeletal muscle but not in placenta, lung, kidney and pancreas. In skin fibroblasts and skeletal muscle, 3.4-kb mRNA was the major species, whereas 1.4-kb mRNA was dominant in heart, brain, and liver. The sequence analysis suggested that the two mRNA species arise from alternative polyadenylation and code a single protein of 192 amino acids. No homologous protein sequence was found in a data base. Elucidation of the function of ZAKI-4 gene product will provide new insights into an important role of T3 in various organs.
Highlights
ZAKI-4 was cloned from cultured human skin fibroblasts
We have shown that T3 inhibits the synthesis of glycosaminoglycan [7, 8] and fibronectin [9], and Chait et al [10] demonstrated that it enhances low density lipoprotein degradation
(t 22 h in the absence and 20 h in the presence of T3). These results indicate that T3 induces ZAKI-4 mRNA at the transcriptional level, but de novo protein synthesis is required for the induction
Summary
ZAKI-4 was cloned from cultured human skin fibroblasts. Northern blot analysis revealed that there were two ZAKI-4 mRNA species (3.4 and 1.4 kilobases (kb)), and they were up-regulated by a physiological concentration of triiodothyronine (T3). We have shown that T3 inhibits the synthesis of glycosaminoglycan [7, 8] and fibronectin [9], and Chait et al [10] demonstrated that it enhances low density lipoprotein degradation. No homologous protein sequence was the method to clone T3-responsive genes in cultured skin fibrofound in a data base. Elucidation of the function of blasts, since it has been successfully employed to identify tran-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
