Regulation of antisense RNA expression during cardiac MHC gene switching in response to pressure overload.
Hypertension has been shown to cause cardiac hypertrophy and a shift in myosin heavy chain (MHC) gene expression from the faster alpha- to slower beta-MHC isoform. The expression of the beta- and alpha-MHC pre-mRNAs, mRNAs, as well as the newly discovered antisense beta-RNA were analyzed in three regions of the normal control (NC) and 12-day pressure-overloaded (AbCon) hearts: the left ventricle apex, left ventricle base, and the septum. The RNA analyses in the AbCon heart targeted both the 5' and the 3' ends of each RNA molecule. beta-MHC mRNA expression significantly increased relative to control in all three regions, regardless of the target site (5' or 3' end). In contrast, beta-MHC pre-mRNA expression in the AbCon heart depended on the site of the measurement (5' vs. 3' end). For example, whereas the pre-mRNA did not change when targeted at the 3' end (last intron), it increased significantly in the AbCon heart when measurement targeted the 5' end (2nd intron) of the 25-kb molecule. Analyses of the antisense beta-RNA revealed that its expression in the AbCon heart was significantly decreased relative to control regardless of its measurement site. A negative correlation was observed between the beta-mRNA expression and the antisense beta-RNA (P < 0.05), suggesting an inhibitory role of antisense RNA on the sense beta-MHC gene expression. In contrast, a positive correlation was observed between the antisense beta-RNA and the alpha-MHC pre-mRNA (P < 0.05). This latter observation along with the alpha-MHC gene position relative to that of the beta-antisense suggest that the alpha-MHC sense and beta-antisense transcription are coregulated likely via common intergenic regulatory sequences. Our results suggest that the increased beta-MHC expression in the AbCon heart not only is the result of increased beta-MHC transcription but also involves an antisense beta-RNA regulation scheme. Although the exact mechanism concerning antisense regulation is not clear, it could involve modulation of both transcriptional activity of the beta-MHC gene and posttranscriptional processing.
Haddad
F
F
Physiology and Biophysics Department, University of California-Irvine, CA 92697-4560, USA. fhaddad@uci.edu
Qin
A X
AX
Bodell
P W
PW
Zhang
L Y
LY
Guo
H
H
Giger
J M
JM
Baldwin
K M
KM
D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics*; D009929:Organ Size / Q000502:physiology; D012313:RNA; D016372:RNA, Antisense / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
C034477:RNA primers; D016372:RNA, Antisense; D012313:RNA; D018995:Myosin Heavy Chains