Co-overexpression of DEAD box protein rck/p54 and c-myc protein in human colorectal adenomas and the relevance of their expression in cultured cell lines.
The RCK gene was cloned through a study of the breakpoint of the t(11;14)(q23;q32) chromosomal translocation observed in a human B-cell lymphoma and overexpression of the protein (rck/p54) due to the translocation was shown to be associated with malignant transformation. The rck/p54 protein belongs to the DEAD box protein/RNA helicase family, which has a variety of functions such as translation initiation, pre-mRNA splicing and ribosome assembly. It is considered that rck/p54 protein may have significant effects on the mRNA structure of genes associated with cell proliferation, facilitating protein synthesis. Expression of rck/p54 in colorectal adenomas, which are a premalignant lesion of colorectal cancer, was examined by Western blot analysis and immunohistochemistry. The rck/p54 protein was found to be overexpressed in tumor tissues resected from 17 of 26 cases (65.4%) of colorectal adenomas and 13 of 14 c-myc-positive cases (92.8%) also co-overexpressed rck/p54 protein. Thus, a significant correlation between rck/p54 and c-myc co-overexpression was found (Spearman's rank correlation, P = 0.0018). We demonstrate that overexpression of rck/p54 in two different cell lines, COS 7 and human colorectal cancer cell line SW480, caused an increase in c-myc protein levels by enhancement of its translation efficiency and/or stabilization of its mRNA. These results suggest that rck/p54 of the DEAD box protein/RNA helicase family may contribute to cell proliferation and carcinogenesis in the development of human colorectal tumors at the translational level by increasing synthesis of c-myc protein.
Hashimoto
K
K
Second Department of Internal Medicine, Osaka Medical College, Daigaku-cho, Takatuki, Osaka 569-8686, Japan.
Nakagawa
Y
Y
Morikawa
H
H
Niki
M
M
Egashira
Y
Y
Hirata
I
I
Katsu
K
K
Akao
Y
Y
D000236:Adenoma / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D000368:Aged; D020816:Amino Acid Motifs; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D018807:Polymorphism, Single-Stranded Conformational; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D012316:RNA Nucleotidyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D012316:RNA Nucleotidyltransferases; C094683:DDX6 protein, human; D053487:DEAD-box RNA Helicases