IDENTIFICATION OF REGIONS ON THE HEMAGGLUTININ-NEURAMINIDASE PROTEIN OF HUMAN PARAINFLUENZA VIRUS TYPE-2 IMPORTANT FOR PROMOTING CELL-FUSION

The hemagglutinin-neuraminidase (HN) and fusion (F) glycoproteins of t wo paramyxoviruses, human parainfluenza virus type 2 (PIV2) and simian virus 41 (SV41), were expressed in HeLa cells by transfecting with re combinant plasmid harboring each glycoprotein gene. Expressed F protei ns could not induce cell fusion by themselves, but evoked prominent ce ll fusion when coexpressed with homologous HN proteins. It was also pr oved that PIV2 HN protein could weakly promote SV41 F-mediated cell fu sion. By analyzing the fusion-promoting function of chimeric HN protei ns of PIV2 and SV41, it was revealed that the N-terminal region (about 16% of total amino acids) of either PIV2 HN or SV41 HN protein could define the type-specific fusion-promoting function for homologous F pr otein. Analyses of additional chimeras indicated that the N-terminal r egion in PIV2 HN protein (designated region I, consisting of 94 amino acids) could be reduced to a 58-amino-acid region (region I') which wa s located at the membrane-proximal end of the ectodomain. Furthermore, PIV2 HN protein proved to promote cell fusion mediated by PIV4A F pro tein. Unexpectedly, analyses of another set of chimeras revealed that the promoting function of PIV2 HN protein for PIV4A F-mediated cell fu sion was not merely carried by its region I but also by another region ranging from residue 148 to 209 (region II). Finally, it was indicate d that regions I' (in the presumed stalk domain) and II (in the globul ar head) in PIV2 HN protein might play important roles in promoting ce ll fusion mediated by the F proteins. (C) 1995 Academic Press, Inc.