Avian Paramyxovirus - Virology

Virology

APMV contain 6–10 tandemly linked genes that encode at least 7 and as many as 12 different proteins. The gene arrangement is 3'Leader-N-P-M-F-HN-L-Trailer-5'for all the serotypes except for APMV-6 which has a unique SH gene between F and HN. The 3′ and 5′ ends of the genome contain short respective extragenic ‘leader’ and ‘trailer’, regions. The following are the important proteins produced nucleoprotein (N), a phosphoprotein (P), a matrix protein (M), a fusion glycoprotein (F), an attachment glycoprotein that in the case of the APMVs is a hemagglutinin-neuraminidase (HN), and a large polymerase protein (L) The viral RNA polymerase begins transcription at the 3′ end and proceeds downstream in a sequential manner generating individual mRNAs encompass by gene-start (GS) and gene-end (GE) signals that flank each gene. The genome is transcribed sequentially from N to L with reduction in expression levels along its length. Non-coding intergenic sequences (IGS) are present between gene boundaries and are not copied into mRNAs. N encodes nucleocapsid protein that associates with the genomic RNA forming the nucleocapsid. M encodes the Matrix protein required for viral assembly. HN and F form the viral coat, and are required for viral entry into cells and also determine the antibody response. The phosphoprotein P is a cofactor for L. The atomic structure is now available for two of them, F and HN.