FIGURE 8.

APOBEC2 is a soluble homotetramer showing little evidence of RNA binding. A, APOBEC2 from gastrocnemius muscle extracts was eluted from a calibrated Sephadex gel filtration column and detected by Western blotting following SDS-PAGE. Preincubation of the extract with RNase did not affect the APOBEC2 elution profile (not shown). B, MBP-APOBEC1 (A1) and MBP-APOBEC2 (A2) were compared for binding to AU repeat RNA and apolipoprotein B targets. The MBP fusion proteins produced from E. coli were incubated at two different concentration (differing 10-fold) with ³²P-labeled RNA. After UV cross-linking and digestion with RNase, samples were subjected to SDS-PAGE, and proteins were identified by staining (Total), whereas cross-linked RNA (X-linked) was detected by autoradiography.