Abstract
Six cDNA sequences encoding the putative HLA-DR associated protein II ( PHAPII), which binds the intracellular domain of HLA class II molecules, were isolated from a mouse embryo cDNA library using a PCR technique. Based on the N-terminal structure of the predicted proteins, these cDNA clones were divided into two groups, PHAPII a and PHAPII β based on sequence similarity to the known PHAPII homologue template activating factors (TAF) -Iα and TAF-I β. Four PHAPIIα cDNA clones (1015, 925 819 and 409 bp) were amplified with the same oligonucleotide primers and two cDNA clones (920 and 869 bp) were amplified with other primers. The 925-bp cDNA, designated PHAPII a, and the 820-bp cDNA, designated PHAPII β, encoded the 289-amino acid TAF-Iα and 177-amino acid TAF-I β, respectively. Although the other four clones were almost identical to PHAPIIα except for small insertions or deletions, the predicted proteins were markedly smaller than the authentic PHAPII due to premature termination of translation or deletion of some of the coding region. Sequence comparison and the fact that the inserted nucleotide sequence included consensus sequences for intron 5'-donor and 3'-acceptor sites suggested that these isoforms are generated by alternative splicing of a single gene. The developmental expression and tissue distributions revealed that both proteins are ubiquitously expressed in different tissues and throughout embryonic development of mouse.
