Ribosomal skipping (kw:KW-1197)

Ribosomal "skipping" is an alternate mechanism of translation in which a specific viral peptide prevents the ribosome from covalently linking a new inserted aa, and let it continue translation. This result in apparent co-translational cleavage of the polyprotein.
This process is induced by a "2A-like", or CHYSEL (cis-acting hydrolase element) sequence. This sequence comprises a non-conserved sequence of amino-acids with a strong alpha-helical propensity followed by the consensus sequence -D(V/I)ExNPG P, where x= any amino acid. The apparent cleavage occurs between G and P.
Ribosomal "skipping" has been observed only in +ssRNA and dsRNA viruses, whose hosts are animals, plant or insect. The conserved motif has been identified also in trypanosoma and in some fungus proteins.

Ribosomal "skipping" is functioning both in vitro and in vivo when translated by eukaroytic ribosomes, but is inactive when translated by prokaryotic ribosomes.

Family	Genus	Virus	Sequence ( \|= apparent cleavage )	Frequency	UniProt
Picornaviridae	Aphthovirus	Foot-and-mouth disease virus	PSDARHKQRIVAPAKQLLNFDLLKLAGDVESNPG\|P	99%	Q9DLK1
	Avisivirus	Avisivirua A	ARRTLEWARREVGAIDETDHKDILLGGDIEENPG\|P	99%	M4PJD6
	Avihepatovirus	Duck hepatitis A virus	RLKTLAFELNLEIESDQIRNKKDLTTEGVEPNPG\|P	99%	Q0ZQM1
	Cardiovirus	Encephalomyocarditis virus	VREENVFGLYRIFNAHYAGYFADLLIHDIETNPG\|P	99%	Q66765
	Cosavirus	Cosavirus A	IMADSVLPRPLTRAERDVARDLLLIAGDIESNPG\|P	99%	B8XTP8
	Erbovirus	Equine rhinitis B virus 1	SEPIPEATLSTILSEGATNFSLLKLAGDVELNPG\|P	99%	Q66776
	Erbovirus	Seneca Valley virus	RYKNARAWCPSMLPFRSYKQKMLMQSGDIETNPG\|P	99%	Q155Z9
	Hunnivirus	Hunnivirus A	CPRPGMAIDPPAQSSGATNFSLLRLAGDVELNPG\|P	99%	F4YYF3
	Kunsagivirus	Kunsagivirus A	SPRSLLHFLIGRPRPRVPPSPSLLLSGDVEPNPG\|P	NA	S4VD62
	Mischivirus	Mischivirus A	DSYPASGEEEEDDFHDMEDHSDILLGGDVEENPG\|P	99%	I3VR62
	Mosavirus	Mosavirus A2	TNSRAKLMVDEDYVIQRSAHRSVLLDGDVESNPG\|P	99%	X2L6K2
	Pasivirus	Pasivirus A1	DIPSFQRDFINWLGSKEELQNMILQCGDVEQNPG\|P	99%	I6YQK4
	Teschovirus	Porcine teschovirus 1	EGLSSAMTVMAFQGPGATNFSLLKQAGDVEENPG\|P	99%	Q9WJ28
Iflaviridae	Iflavirus	Infectious flacherie virus	NYPLVPSIGNVARTLTRAEIEDELIRAGIESNPG\|P	99%	O70710
Tetraviridae	Betatetravirus	Thosea asigna virus	RSRRLRGPRPQNLGVRAEGRGSLLTCGDVEENPG\|P	94-99%	Q9YK87
Dicistroviridae	Cripavirus	Cricket paralysis virus	FQQWKLVSSNDECRAFLRKRTQLLMSGDVESNPG\|P	88%	Q9IJX4
Reoviridae	Rotavirus	Human rotavirus C	LKKHNGAGYPLIVANSKFQIDKILISGDIELNPG\|P	82%	Q9PY95
Reoviridae	Cypovirus	Lymantria dispar cypovirus 1	TDFLSMTAFDFQQAVFRSNYDLLKLCGDVESNPG\|P	99%	Q91ID7

References
Luke GA, de Felipe P, Lukashev A, Kallioinen SE, Bruno EA, Ryan MD.
*Occurrence, function and evolutionary origins of '2A-like' sequences in virus genomes*.
J Gen Virol. 2008 Apr;89(Pt 4):1036-42. PubMed

Doronina VA, de Felipe P, Wu C, Sharma P, Sachs MS, Ryan MD, Brown JD.
Dissection of a co-translational nascent chain separation event.
Biochem Soc Trans. 2008 Aug;36(Pt 4):712-6. PubMed

Martin D. Ryan, Michelle Donnelly, Arwel Lewis, Amit P. Mehrotra, John Wilkie, David Gani.
A Model for Nonstoichiometric, Cotranslational Protein Scission in Eukaryotic Ribosomes.
Bioorganic Chemistry, Volume 27, Issue 1, February 1999, 55-79 link