FIG. 4.

Enrichment and selection of a cDNA encoding a UBF2 fusion protein. (Top) Comparison of amino acid sequences from HMG box 2 of UBF1 and UBF2 isoforms. UBF1 and UBF2 are derived from the same gene by differential splicing; UBF2 contains a 37-amino-acid deletion in HMG box 2. The dashes represent missing amino acids. (Bottom) Amino acid sequence of the carboxyl terminus of fu UBF2, selected in the screen, compared to the carboxyl-terminal sequence of wt UBF1 and wt UBF2. fu UBF2 encodes a fusion between the UBF2 protein, with a carboxyl-terminal truncation of 16 amino acids, and 41 novel carboxyl-terminal amino acids (underlined) derived from out-of-frame translation of ribosomal protein L31. cd UBF2 was constructed to represent the truncated UBF2 protein without the 41-amino-acid carboxyl-terminal extension. The wt UBF1 and wt UBF2 clones were isolated from a human placenta cDNA library.