bPML nuclear bodies and their associated functions are part of an intrinsic cellular mechanism aimed at maintaining transcriptional control over viral gene expression and preventing replication of invading viruses. To overcome these barriers, many viruses express early nonstructural, multifunctional proteins to support the viral replication cycle or modulate host immune responses. Virion proteins constituting the invading particle are traditionally investigated for their role in transport during entry or egress and in the assembly of new virions. The additional functions of virion proteins have largely been ignored, in contrast to those of their nonstructural counterparts. A number of recent reports suggest that several virion proteins may also play vital roles in gene activation processes, in particular by counteracting intrinsic immune mechanisms mediated by the PML nuclear body-associated cellular factors Daxx, ATRX, and Sp100. These virion proteins share several features with their more potent nonstructural counterparts, and they may serve to bridge the gap in the early phase of an infection until immediate early viral gene expression is established. In this review, we discuss how virion proteins are an integral part of gene regulation among several viral families and to what extent structural proteins of incoming virions may contribute to species barrier, latency, and oncogenesis.W hen viral genetic information is transferred from cell to cell, it must be compacted and transcriptionally inactivated for storage in the viral capsid during transport. This process needs to be actively reversed upon infection against cellular transcriptional repression through intrinsic antiviral mechanisms. An important factor in the cellular control of viral gene expression is death domain-associated protein (Daxx). Daxx was initially described as a modulator of apoptotic signaling (1), but recent reports suggest that Daxx plays an active role in gene regulation by repressing or modulating transcription through chromatin remodeling (2, 3). Daxx mainly cooperates with alpha-thalassemia retardation syndrome x-linked (ATRX), a putative member of the SNF2 family of ATP-dependent chromatin-remodeling proteins. In this repressive complex, ATRX acts as the core ATPase subunit, while Daxx is the targeting factor, leading to histone deacetylase (HDAC) recruitment (4-6).Daxx is found associated with the promyelocytic leukemia protein nuclear body (PML-NB) or chromatin. Association with PML-NB alleviates gene repression and activates apoptosis, while chromatin-bound Daxx represses transcription (7-9). It has been long established that PML-NBs are nuclear structures with antiviral activity, accumulating an expanding number of transient or constitutive cellular factors involved in transcriptional control, chromatin remodeling, genome integrity, apoptosis, and tumor suppression (10). Moreover, several PML-NB constituents can be induced by type I and II interferon (IFN), resulting in increased antiviral activity by attenuating viral gene exp...