Ebola virus VP35 has novel NTPase and helicase-like activities

Shu, Ting; Gan, Tianyu; Bai, Peng; Wang, Xiaotong; Qian, Qi; Zhou, Hui; Cheng, Qi; Qiu, Yang; Yin, Lei; Zhong, Jin; Zhou, Xi

Because some virus-encoded RNA helix-unwinding proteins can also unwind DNA helix and/or RNA-DNA hybrids (22) , we sought to examine the possibility for EBOV VP35. To this end, we generated four different nucleic acid helix substrates, which are RNA helix R*/R, DNA helix D*/D, RNA-DNA hybrids with longer RNA or DNA strand (D/R* or R*/D, as illustrated in Figure 5A -D, upper panels), respectively. Each of the four different helix substrates was incubated with MBP-VP35 and subjected to the standard helix-unwinding assay. Our results showed that VP35 could unwind RNA helix R*/R ( Figure 5A ) and RNA-DNA hybrid D/R* ( Figure 5C ), both of which have longer RNA strands. On the other hand, VP35 could not unwind DNA helix D*/D ( Figure 5B ) or RNA-DNA hybrid R*/D ( Figure 5D ) that have longer DNA strand. This finding indicates that the helix-unwinding activity of EBOV VP35 requires the presence of protruded single-stranded RNA in the helix substrates, which is consistent with its potential roles in the RNA replication and/or transcription of an RNA virus.