TABLE 1.

Phosphorimager analyses of data on DNA methylation^a

Restriction enzyme	Frag-ment	Relative intensity in cell line:
		BHK21	BHK21-λ7	BHK21-λ10	BHK21-λ12	BHK21-λ18	BHK21-λ27
HpaII	1	1.00	1.36	1.35	1.78	1.39	0.92
	2	1.00	2.57	2.16	2.88	2.56	1.68
	3	1.00	3.07	1.80	3.21	2.65	1.71
	4	1.00	1.78	1.62	1.99	1.41	1.41
	5	1.00	2.08	1.61	1.77	1.55	1.30
	6	1.00	1.82	1.80	1.52	1.21	1.19
	7	1.00	1.57	1.38	0.81	1.26	1.17
	8	1.00	1.43	1.55	1.03	1.25	1.16
	9	1.00	0.63	0.69	0.89	0.93	1.08
	10	1.00	0.29	0.49	0.54	0.47	0.75
	11	1.00	0.54	0.58	0.88	0.85	0.91
	12	1.00	0.23	0.27	0.35	0.37	0.39
HhaI	1	1.00	1.86	2.19	1.97	2.28	1.64
	2	1.00	2.95	2.48	2.88	4.19	1.79
	3	1.00	2.86	2.95	2.78	3.35	2.92
	4	1.00	2.25	2.64	2.73	2.99	2.29
	5	1.00	2.12	1.89	2.46	2.38	2.31
	6	1.00	1.27	1.12	0.77	0.83	1.25
	7	1.00	0.93	0.88	0.78	0.60	0.72
	8	1.00	0.65	0.60	0.48	0.30	0.44
	9	1.00	0.64	0.61	0.60	0.42	0.50
	10	1.00	0.82	0.57	0.60	0.60	0.51
	11	1.00	0.83	0.62	0.52	0.55	0.46
	12	1.00	0.70	0.88	0.86	0.87	0.94
	13	1.00	0.50	0.64	1.00	1.07	0.78
	14	1.00	0.36	0.36	0.58	0.57	0.44
	15	1.00	0.59	0.54	1.01	0.79	1.10
MspI	1	1.00	1.04	1.14	1.23	1.11	1.16
	2	1.00	1.05	0.87	0.97	0.80	0.78
	3	1.00	0.91	0.76	0.56	0.85	0.74

^aAnalyses of the cleavage patterns in the IAPI segments of five different clonal BHK21 cell lines carrying integrated λ DNA are shown. All fragment bands in the autoradiograms of Fig. 5 were numbered from 1 to 12 (HpaII), from 1 to 15 (HhaI), or from 1 to 3 (MspI), from top to bottom, i.e., from high to low molecular mass. The data presented in Fig. 5 were analyzed by quantitating the intensities in individual fragment bands with the aid of a phosphorimager. In comparing fragment band intensities for each individual band in the total cleavage patterns between BHK21 DNA, the internal standard for comparisons, and the DNAs of any of the BHK21-λ clones, the intensity values for the fragments in BHK21 DNA were arbitrarily set to 1.00. The light intensities for the corresponding fragments on the autoradiograms for all of the BHK21-λ clones were then calculated relative to those of the internal BHK21 standard. Thus, intensity comparisons are feasible only by reading the values in Table 1 across. Decreases of values in the lower-molecular-mass bands and increases in the higher-molecular-mass bands were due to increases in DNA methylation. These analyses were performed for the HpaII, HhaI, and MspI cleavage patterns. Since MspI was not sensitive to DNA methylation in the 3′-cytidine residue in the sequence 5′-CCGG-3′, marked changes in relative intensities in the λ DNA-transgenic cell lines were not expected and not observed. The MspI data represented an internal control.