TABLE 3.

Effects of overexpression of the N- and C-terminal domains of Sir3p on telomeric position effect and requirements for enhanced repression: fraction of FOA^R colonies or ADE2 repression upon overexpression of Sir3N or Sir3p^a

Fraction 5-FOARb					ADE2 repressionc
Strain	Genotype	pADH-SIR3N	pADH-SIR3	pADH	Strain	Genotype	pADH-SIR3N	pADH-SIR3	pADH
					UCC3107	SIR+	+++	+++	+
YHR436	SIR+	0.25 (0.16–0.33)	0.34 (0.36–0.3)	0.084 (0.015–0.12)
					UCC3242	sir1	+++	+++	+
YHR434	sir2	<4.0 × 10−5	<4.0 × 10−6	<6.0 × 10−6
					GA506	HHF2	+++	+++	+
YHR440	sir3	<1.0 × 10−5	0.30 (0.42–0.21)	<1.0 × 10−5
					GA509	HHF2-gly17	−	−	−
YHR441	sir4	<2.0 × 10−5	<4.0 × 10−6	<2.0 × 10−5
					GA510	HHF2-gly16	−	−	−
					GA513	HHF2-gln16	−	−	−

^aShown are the frequency of resistance to 5-FOA in strains carrying URA3 adjacent to the VII_L telomere and repression of the ADE2 gene adjacent to the V_R telomere. The strains were transformed with the same 2μ-based plasmids as for Table 2. The relevant genotypes of the strains are indicated. 

^bThe mean of the frequency of 5-FOA resistance from three independent transformants is presented; the range of values is given in parentheses. 

^c+++, strong red color (strong repression); +, red-white color; −, white color (complete derepression).