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. 1997 Feb 18;94(4):1064–1068. doi: 10.1073/pnas.94.4.1064

Figure 4.

Figure 4

CKII-mediated phosphorylation of C1 hnRNP protein is not stimulated by RNA. C1 hnRNP protein was incubated for 2 hr at 30°C in the same buffer as used in Fig. 1 (but no nuclear extract) in the presence or absence of human CKII (Boehringer Mannheim) at a final concentration of 15 milliunits/ml, and in the presence or absence of HeLa nuclear extract RNA, at a final concentration of 75 μg/ml. Lanes: 1, C1 hnRNP protein and purified CKII; 2, C1 hnRNP protein, no CKII; 3, C1 hnRNP protein and CKII plus nuclear extract RNA; 4, C1 hnRNP protein plus nuclear extract RNA. Results similar to those shown in the figure were obtained when the incubation period of C1 hnRNP protein with CKII was 30 min or 1 hr. In addition to showing that the phosphorylation of C1 hnRNP protein by CKII is not stimulated by RNA (lanes 1 vs. 3), this experiment also indicates that the C1 hnRNP protein does not undergo autophosphorylation under these experimental conditions, either in the presence or absence of RNA (lanes 2 and 4).