Ambisense polarity of genome RNA of orthomyxoviruses and coronaviruses

Table 1 RNA segments of influenza A virus genome and encoded polypeptides

Viral RNA segments and their length (nt)1	Positive sense polypeptides (mol. wt., kDa)2	Negative stranded polypeptides, NSPs (mol. wt.; a.a.)3
PB1 (2341)	PB1 (86.6); PB1-N40 (89.4); PB1-F2 (10.5)	NSP1 (174, 239)
PB2 (2341)	PB2 (85.7); PB2-S1 (55)	NSP2 (116, 121, 130, 137)
PA (2223)	PA (84.2); PA-X (29); PA-N155 (62); PA-N182 (60)	NSP3 (95, 109)
HA (1778)	HA (61.5)	NSP4 (n.d.)
NP (1565)	NP (56.1); eNP (56.8)	NSP5 (117, 154)
NA (1413)	NA (50.1); NA43 (48.6)	NSP6 (91, 154)
M (1097)	M1 (27.8); M2 (11); M42 (13)	NSP7 (99, 102, 109)
NS (890)	NS1 (26.8); NEP (14.2); NS3 (21); tNS1 (17)	NSP8 (93, 167, 216)

¹RNA segments and nucleotide (nt) calculations were made for the A/PR8/34 (H1N1) virus.

²Canonical influenza A virus polypeptides synthesized through the negative genome strategy (Figure 1; for review see[1]).

³Negative stranded genomic open reading frames (ORFs) and predicted negative stranded proteins (NSPs) have been calculated for A/PR8/34 (H1N1) and A/Aichi/2/68 (H3N2) viruses[3-8]. Negative stranded ORFs were identified by in silico approach using the Open Reading Frame Finder program (https://www.ncbi.nlm.nih.gov/orffinder/). These ORFs can be realized through the positive genome strategy. The amino acid length (a.a.) of NSPs were based on the data presented mainly in ref.[8]. A.a. values reflect variations among human, avian and other mammalian virus strains. N.d. means the absence of ORFs longer than 90 a.a. NSP: Negative stranded protein.