Multiple sequence-directed possibilities provide a pool of nucleosome position choices in different states of activity of a gene

Table 1 Comparison of nucleosome positions on SNR6, mapped in this study with those reported in other studies

No.	Position (bps) This study	Similar to position (bp)	Comments	Ref. No.
1.	-545 to -368	-537 to -367	In vivo, in the presence of bound TFIIIC	39
2.	-368 to -78	-367 to -214	In vivo, in the presence of bound TFIIIC	39
3.	-656 to -453		In vitro, sequence-directed
4.	-453 to -241		In vitro, sequence-directed
5.	-241 to -78	-240 to -70	In vivo, in the presence of bound TFIIIC	37
6.	-125 to +25	-194 to -16	In vivo, in the absence of bound TFIIIC	39
		-120 to +28	In vivo, under repression	37
7.	-110 to +45	-116 to +40	Predicted	26
8.	-90 to +65	Positions 8–10 together as bp -78 to + 110 in the plasmid
9.	-60 to +95	p-539H6, Figure 1B, sequence-directed.
10.	-40 to +115	Positions 9–15 together as bp -50 to + 316 in the plasmid
11.	-20 to +125	pCS6, Figure 1C, sequence-directed.
12.	+51 to +196	+48 to +192	In vitro, TFIIIC-dependent	3
		+94 to +198	In vivo, in the presence of bound TFIIIC	59
13.	+71 to +216	+71 to +227	Predicted	26
		+85 to +206	In vivo, in the absence of bound TFIIIC	39
14.	+91 to +236		In vitro, sequence-directed
15.	+101 to +256		In vitro, sequence-directed

All 15 positions in Column 2 are sequence-directed as nucleosomes are assembled in the absence of any transcription or chromatin assembly factors. Positions 1 to 5 are mapped by the low-resolution technique (Figure 1B) and fall in the upstream region; the rest of the positions on the gene region (6 to 15) are mapped by the higher resolution Exo III analysis (Figures 5 and 6) in this study. Positions 3 to 5, 8, 9, 14 and 15 represent the register R1 while R2 is constituted by the positions 1, 2 (or 3, 4), 6, 12 and 13. Arrangement of nucleosomes in active state R3 is generated by the positions 1, 2 (or 3, 4), 5 and 12 giving a nucleosome-free region flanked by positioned nucleosomes.

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