TABLE 2.

Assay systems used to monitor various tRNA modifications in −1 frameshifting

Site	Organism	Mutants used	Heptameric sequencea	tRNA in P-site	Modification tested in P-site tRNA	tRNA in A-site	Modification tested in A-site tRNA
HIV	S. typh.	miaA	U-UUU-UUA	tRNAPheGAA	ms2io6- of ms2io6A37	tRNALeucmnm5UmAA	ms2io6- of ms2io6A37
HIV	S. typh.	miaB	U-UUU-UUA	tRNAPheGAA	ms2- of ms2io6A37	tRNALeucmnm5UmAA	ms2- of ms2io6A37
HIV	S. typh.	miaE	U-UUU-UUA	tRNAPheGAA	o6- of ms2io6A37	tRNALeucmnm5UmAA	o6- of ms2io6A37
HIV	S. typh.	truA	U-UUU-UUA	tRNAPheGAA	Ψ39	tRNALeucmnm5UmAA	Ψ39
HIV	E. coli	truB	U-UUU-UUA	tRNAPheGAA	Ψ55	tRNALeucmnm5UmAA	Ψ55
argI	S. typh.	miaA, miaB	G-UUU-UAU	tRNAPheGmAA	ms2io6- of ms2io6A37	tRNATyrQUA	ms2io6- of ms2io6A37
argI	S. typh.	tgt	G-UUU-UAU	tRNAPheGmAA	None	tRNATyrQUA	Q34
MMTV	E. coli	mnmA	A-AAA-AAC	tRNALysmnmn5s2UUU	s2- of mnm5s2U34	tRNAAsnQUU	None
MMTV	E. coli	mnmE	A-AAA-AAC	tRNALysmnmn5s2UUU	mnm5- of mnm5s2U34	tRNAAsnQUU	None
MMTV	S. typh.	tgt	A-AAA-AAC	tRNALysmnmn5s2UUU	None	tRNAAsnQUU	Q34
MMTV	E. coli	truA	A-AAA-AAC	tRNALysmnmn5s2UUU	Ψ39	tRNAAsnQUU	Ψ39
MMTV	E. coli	truB	A-AAA-AAC	tRNALysmnmn5s2UUU	Ψ55	tRNAAsnQUU	Ψ55
HIV	S. cerev.	trm5	U-UUU-UUA	tRNAPheGmAA	Y-base	tRNALeuU?AA	m1G37
L-A	S. cerev.	trm5	G-GGU-UUA	tRNAGlyU?CC	None	tRNALeuU?AA	m1G37

^aThe first triplet denotes the codon in the P-site and the next triplet the codon in the A-site, if the frameshifting occurred as postulated by the “simultaneous slippage model.”