MAMMALIAN CAP INTERACTS WITH CAP, CAP2, AND ACTIN

We previously identified human CAP, a homolog of the yeast adenylyl cy clase-associated protein. Previous studies suggest that the N-terminal and C-terminal domains of CAP have distinct functions. We have explor ed the interactions of human CAP with various proteins. First, by perf orming yeast two-hybrid screens, we have identified peptides from seve ral proteins that interact with the C-terminal and/or the N-terminal d omains of human CAP. These peptides include regions derived from CAP a nd BAT3, a protein with unknown function. We have further shown that M BP fusions with these peptides can associate in vitro with the N-termi nal or C-terminal domains of CAP fused to GST. Our observations indica te that CAP contains regions in both the N-terminal and C-terminal dom ains that are capable of interacting with each other or with themselve s. Furthermore, we found that myc-epitope-tagged CAP coimmunoprecipita tes with HA-epitope-tagged CAP from either yeast or mammalian cell ext racts. Similar results demonstrate that human CAP can also interact wi th human CAP2. We also show that human CAP interacts with actin, both by the yeast two-hybrid test and by coimmunoprecipitation of epitope-t agged CAP from yeast or mammalian cell extracts. This interaction requ ires the C-terminal domain of CAP, but not the N-terminal domain. Thus CAP appears to be capable of interacting in vivo with other CAP molec ules, CAP2, and actin. We also show that actin co-immunoprecipitates w ith HA-CAP2 from mammalian cell extracts. (C) 1996 Wiley-Liss, Inc.