MicroRNA 34a contributes to virus-mediated apoptosis through binding to its target gene Bax in influenza A virus infection.
OBJECTIVE
Influenza A virus is a cytolytic virus that induces apoptosis in numerous cell types. However, molecular mechanism of cell apoptosis induced by influenza A virus is not well understood. The present study was aimed to investigate the molecular mechanism of miR-34a involved in influenza A virus induced apoptosis.


METHODS
Firstly, microRNA array was used to select miRNAs involved in influenza A virus infection. Then, Luciferase reporter assay and western blot were carried to determine the target gene of miR-34a. Finally, miR-34a mimic was transfected in influenza A virus-infected A549 cells, and western blot was used to test the function of miR-34a and its target gene in in influenza A virus infection.


RESULTS
miR-34a was found significantly down-regulated in influenza A virus-infected A549 cells and was further confirmed by qRT-PCR in vitro and in vivo (P<0.01). Next, transfection miR-34 mimic/inhibitor in influenza A virus-infected A549 cells showed that overexpression of miR-34a could inhibit influenza virus-induced apoptosis. Furthermore, target prediction analysis revealed that miR-34a complemented to the 3'-UTR of Bax mRNA. Luciferase reporter assay and western blot confirm that miR-34a directly targeted Bax. Moreover, we detected influenza virus infection enhanced the luciferase reporter translational activity in A549 cells transfected with the construct with Bax 3'-UTR encoding miR-34a binding site. However, western blot analysis showed that the up-regulation of Bax protein level was significantly reversed by overexpression miR-34a.


CONCLUSIONS
It is, therefore, concluded that influenza virus infection regulated pro-apoptotic Bax expression through miR-34a downregulation, which might be the partial mechanism of influenza virus-induced cell apoptosis.
Department of Laboratory Medicine, Huaihe Hospital of Henan University, Kaifeng 475000, Henan, China. Electronic address: ndoublefan@sina.com.
Niannian
N
Fan
Department of Laboratory Medicine, Huaihe Hospital of Henan University, Kaifeng 475000, Henan, China.
Jiantao
J
Wang
D000072283:A549 Cells; D000293:Adolescent; D000328:Adult; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D018390:Gene Targeting / Q000379:methods*; D057809:HEK293 Cells; D006801:Humans; D009980:Influenza A virus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D007251:Influenza, Human / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D008297:Male; D035683:MicroRNAs / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D011485:Protein Binding / Q000502:physiology; D055815:Young Adult; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D051028:bcl-2-Associated X Protein
Bax; Cell apoptosis; Influenza A virus; miR-34a