Research

Ex vivo promoter analysis of antiviral heat shock cognate 70B gene in Anopheles gambiae

Seokyoung Kang¹ , Cheolho Sim² , Brian D Byrd^1,3 , Frank H Collins⁴ and Young S Hong¹

¹  Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana 70112, USA

²  Department of Entomology, the Ohio State University, Columbus, Ohio 43210, USA

³  Environmental Health Sciences, Western Carolina University, Cullowhee, NC 28723, USA

⁴  The Center for Global Health and Infectious Diseases, University of Notre Dame, Notre Dame, IN 46556, USA

author email corresponding author email

Virology Journal 2008, 5:136doi:10.1186/1743-422X-5-136

Published:	5 November 2008

Abstract

Background

The Anopheles gambiae heat shock cognate gene (hsc70B) encodes a constitutively expressed protein in the hsp70 family and it functions as a molecular chaperone for protein folding. However, the expression of hsc70B can be further induced by certain stimuli such as heat shock and infection. We previously demonstrated that the An. gambiae hsc70B is induced during o'nyong-nyong virus (ONNV) infection and subsequently suppresses ONNV replication in the mosquito. To further characterize the inducibility of hsc70B by ONNV infection in An. gambiae, we cloned a 2.6-kb region immediately 5' upstream of the starting codon of hsc70B into a luciferase reporter vector (pGL3-Basic), and studied its promoter activity in transfected Vero cells during infection with o'nyong-nyong, West Nile and La Crosse viruses.

Results

Serial deletion analysis of the hsc70B upstream sequence revealed that the putative promoter is likely located in a region 1615–2150 bp upstream of the hsc70B starting codon. Sequence analysis of this region revealed transcriptional regulatory elements for heat shock element-binding protein (HSE-bind), nuclear factor κB (NF-κB), dorsal (Dl) and fushi-tarazu (Ftz). Arbovirus infection, regardless of virus type, significantly increased the hsc70B promoter activity in transfected Vero cells.

Conclusion

Our results further validate the transcriptional activation of hsc70B during arbovirus infection and support the role of specific putative regulatory elements. Induction by three taxonomically distinct arboviruses suggests that the HSC70B protein may be expressed to cope with cellular stress imposed during infection.