The viral proteins A1L, A2L, G8R, and H5R positively modulate vaccinia virus late gene expression. Host-encoded proteins hnRNP A2 and RBM3 may also interact with these viral factors to influence late gene expression. In these studies, a yeast two-hybrid screen and in vitro pulldown and crosslinking experiments were used to investigate protein--protein interactions among these factors. These studies confirmed a previous observation that G8R interacts with itself and A1L. However, self-interactions of A1L and H5R, and interactions between A2L and G8R, A2L and H5R, and H5R and G8R were also observed. In addition, the proteins hnRNP A2 and RBM3 both showed some interaction with A2L. Illustration of these interactions is a step toward understanding the architecture of the late gene transcription complex as it occurs in poxviruses.

In an adenosine triphosphate (ATP)-dependent process, the hSWI/SNF chromatin remodeling complex functions to alter chromatin structure, thereby regulating transcription factor access to DNA. In addition to interactions with transcription factors and recognition of acetylated histone residues, the chromatin remodeling activity of hSWI/SNF has also been shown to respond to a variety of cell signaling pathways. Our results demonstrate a novel interaction between the serine/threonine kinase Akt and members of the hSWI/SNF chromatin remodeling complex. Activation of Akt in HeLa cells resulted in its association with hSWI/SNF subunits: INI1, BAF155 and BAF170, as well as actin. BAF155 became preferentially recognized by an antibody that detects phosphorylated Akt substrates upon activation of Akt, suggesting that BAF155 may be an in vivo target for phosphorylation by Akt. Glutathione-S-transferase (GST) pulldown experiments demonstrated that INI1 and BAF155 were both capable of directly interacting with Akt. Finally, in vitro kinase assays provided additional evidence that BAF155 and potentially INI1 are substrates for Akt phosphorylation. These data provide the first evidence that Akt signaling may modulate function of the hSWI/SNF complex.