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Identification of in vivo P ‐glycoprotein mRNA decay intermediates in normal liver but not in liver tumors
Author(s) -
Lee Chow H.,
Rehaume Vicki E.,
Shandro Janis
Publication year - 2005
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.20313
Subject(s) - messenger rna , biology , microbiology and biotechnology , gene , coding region , in vivo , untranslated region , gene expression , biochemistry , genetics
Post‐transcriptional regulation at the level of mRNA stability is one important mechanism for over‐expression of P ‐glycoprotein (Pgp) genes observed in cultured cells and in animals. A previous study has shown that mRNA half‐lives for Pgp genes in normal liver were less than 2 h, in contrast to greater than 12 h measured in a transplantable liver tumor line. This lower turnover rate of Pgp mRNA may, in large part, contribute to the abundance of Pgp mRNA in liver tumors. The current study sought to investigate the underlying mechanism for the lower turnover rate of Pgp 2 mRNA previously determined in liver tumors. As a first approach, we set out to understand the Pgp 2 mRNA decay in both normal liver and liver tumors by first identifying and characterizing Pgp 2 mRNA degradation intermediates. In this study, we showed that the sensitive ligation‐mediated polymerase chain reaction (LM‐PCR) method can be used to detect a homogenous pool of in vitro transcribed RNA down to 0.4 ng. By employing gene‐specific primers in the LM‐PCR method, we successfully identified four Pgp 2 mRNA decay intermediates in normal liver. All four decay intermediates detected correspond to the 5′ coding region of Pgp 2 mRNA, and surprisingly no decay intermediates which correspond to 3′ untranslated region, 3′ coding region or middle coding region were found using LM‐PCR. The identified decay intermediates are unique to the normal liver as they were absent or present at very low level in all three liver tumor samples analyzed. This observation supports our previous findings that the Pgp mRNA turnover rate is lower in liver tumors than in normal liver. These findings have implications for our understanding of the regulation of Pgp mRNA turnover in normal and malignant tissues. © 2005 Wiley‐Liss, Inc.