FIG. 6.

The OCTA mutation upstream of the μs poly(A) signal increases poly(A) signal use but does not affect B-cell-plasma cell regulation. The AAUAAA core upstream element is shown in uppercase letters and is underlined. The sequence 38 nt upstream from this core element is shown (see also Fig. 1B). The upstream sequence that matches the consensus Oct1/2 protein binding site is shown below (octamer) (9), and the nucleotide changes made in the OCTA mutation are shown. Above the Cμ sequence are the consensus U1A binding site (U1A) and the nucleotide changes in the “8s” mutation (33). The matches between the Cμ sequence and that of the consensus octamer and U1A sequences are indicated by vertical lines. The pA/splice expression ratios for the Cμ and OCTA constructs transiently expressed in the M12 B-cell and S194 plasma cell lines were obtained by S1 nuclease analysis of at least three transfections analyzed multiple times.