Precursor of human adenovirus core polypeptide Mu targets the nucleolus and modulates the expression of E2 proteins

Abstract

We have examined the subcellular localization properties of human adenovirus 2 (HAdV-2) preMu and mature Mu (pX) proteins as fusions with enhanced green fluorescence protein (EGFP). We determined that preMu is exclusively a nucleolar protein with a single nucleolar accumulation signal within the Mu sequence. In addition, we noted that both preMu-EGFP and Mu-EGFP are excluded from adenovirus DNA-binding protein (DBP)-rich replication centres in adenovirus-infected cells. Surprisingly, we observed that cells in which preMu-EGFP (but not Mu-EGFP) is transiently expressed prior to or shortly after infection with Ad2 did not express late adenovirus genes. Further investigation suggested this might be due to a failure to express pre-terminal protein (preTP) from the E2 region, despite expression of another E2 protein, DBP. Deletion mutagenesis identified a highly conserved region in the C terminus of preMu responsible for these observations. Thus our data suggest that preMu may play a role in modulating accumulation of proteins from the E2 region.

Thermostability/Infectivity Defect Caused by Deletion of the Core Protein V Gene in Human Adenovirus Type 5 Is Rescued by Thermo-selectable Mutations in the Core Protein X Precursor

“…1 Although Cterminal domain of pre-Mu is necessary for its trans-activating function, 42 this activity cannot be carried out by the C-terminal domain alone and also requires the central portion (mature Mu) of the precursor. 42 Since the pre-Mu appears to have function(s) distinct from the ones of the mature protein and is also capable of localizing to the nuclei of the infected cells, 42 it can be hypothesized that the pre-Mu and/or its N-terminal peptide could play an important role in mediating viral assembly in Ad-infected cell. Elucidation of the mechanism whereby mutations in pre-Mu suppress the effect of pV deletion is currently underway.…”

“…Some recent evidence, however, suggests that the C-terminal peptide of pre-Mu is essential for its repression of the late genes (VI) in adenovirus-infected cells. 42 Since the suppressor mutations of the Ad5-dV/TSB mapped in the pre-Mu coding sequence are distal to the precursor processing sites, they are unlikely to affect processing of the precursor.…”

An Imaging System to Monitor Efficacy of Adenovirus-Based Virotherapy Agents

“…Recent intracellular localization and functional studies of Mu, pV, and pVII were performed with carboxy terminal fusion of EGFP to the native proteins (Lee et al, 2003(Lee et al, , 2004Matthews, 2001). Our attention was drawn to three established observations from these reports:…”

“…1A). PreMu-EGFP was not chosen as a candidate for labeling because it has been shown to block late adenovirus gene expression when expressed concomitantly with adenovirus infection (Lee et al, 2004). In the chimeric expression system, both the native, unmodified core protein and the fusion counterpart were expressed from the same vector.…”

“…In the chimeric expression system, both the native, unmodified core protein and the fusion counterpart were expressed from the same vector. We initially applied the AdEasy system to construct E1 expression vectors under the control of the constitutive cytomegalovirus (CMV) promoter ( (Lee et al, 2003(Lee et al, , 2004Matthews, 2001). …”