Sequence analysis indicated that human p44 shares 97% protein sequence identity with the predicted mouse p44
homolog and 33% identity with the S. cerevisiae eIF3-p33 subunit. p44 binds RNA, as do eIF3 subunits p170 and p66. On Far Western blots, the p44 protein interacted strong and specifically with p170, and weakly with p116/p110, p66, p40 , and itself. Northern blot analysis revealed that p44 is expressed as an approximately 1.4-kb mRNA in HeLa cells.When expressed in mammalian cells, epitope-tagged p42 was incorporated into endogenous eIF3. The authors found that a major fraction of endogenous eIF5 was associated with eIF3, leading them to suggest that a specific interaction between these 2 initiation factors may play an important role in the function of eIF5 during translation initiation.