Effect of TPA on the levels of erythroid, megakaryocytic, and ubiquitous endogenous transcripts of K562 cells.

Northern blot analyses were performed with RNA samples from wild-type K562 cells. Total RNAs were extracted from TPA-untreated cells (0) and from cells preliminarily treated with TPA for 24 and 48 hours (24 and 48). Ethidium bromide (Et. B.) staining revealed 2 bands, which corresponded to the ribosomal RNAs 28S and 18S and the intensity of which correlated with the amount of total RNA loaded on the agarose gel (10 μg). GPA, CD55, CD44, RhAG, Rh, and CD47 probes were prepared and labeled as described in “Materials and methods.” Blots were exposed overnight to Kodak BioMax MS film. With the Rh probe, exposure was performed for 48 hours. Several endogenous transcripts were found for GPA, CD55, CD44, and Rh.