Maxwell Bui-Marinos, University of Calgary

Authors: Mariel Kleer, Jennifer A. Corcoran. Affiliations (for presenter and authors): #1 - Microbiology, Immunology & Infectious Diseases Department, University of Calgary, Calgary, Alberta, Canada. #2 - Charbonneau Cancer Research Institute, University of Calgary, Calgary, Alberta, Canada. #3 - Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.

Suppressing & Conquering

Kaposi's sarcoma-associated herpesvirus (KSHV) causes the rare, inflammatory skin neoplasm, Kaposi's sarcoma (KS). Kaposin, a GC-rich, repetitive polycistron, is abundantly expressed in KS lesions suggesting its importance in tumours. We recently showed that kaposin RNA is nuclear-retained during latent infection but enters the cytoplasm and is minimally translated at late reactivation times. This suggests kaposin may be a bifunctional RNA, deriving function from both the transcript and protein. Overexpression constructs (producing kaposin RNA and KapB protein) elicit the disassembly of processing (p-)bodies, granules that repress inflammatory and tumourigenic mRNAs. This creates a new question; which molecule elicits p-body loss? This study will determine the molecule responsible for p-body disassembly. We created three constructs to uncouple kaposin RNA- and KapB-mediated functions: wild-type, ‘recoded' (authentic KapB, alternatively coded RNA), and ‘nostarts' (authentic RNA, fails to translate KapB). Overexpression of constructs followed by IF-FISH for p-bodies and kaposin RNA showed that both KapB protein and kaposin RNA elicit p-body disassembly. When results were stratified by kaposin RNA staining, the kaposin-positive population showed enhanced disassembly suggestive of a cell autonomous function. To assess non-cell autonomous effects, conditioned media (CM) rich was transferred onto naïve, serum-starved cells. CM treatment from wild-type and nostarts caused p-body size increases while p-body size was unaffected by CM from recoded-expressing cells. These data suggest that KapB protein may promote the release of secretory factors that induce p-body disassembly. Together, this suggests the kaposin gene produces kaposin RNA and KapB protein which each utilize a distinct mechanism to disassemble p-bodies.