More than 120 human papillomaviruses (HPVs) have now been identified and have been associated with a variety of clinical lesions. To understand the molecular differences among these viruses that result in lesions with distinct pathologies, we have begun a MS-based proteomic analysis of HPV-host cellular protein interactions and have created the plasmid and cell line libraries required for these studies. To validate our system, we have characterized the host cellular proteins that bind to the E7 proteins expressed from 17 different HPV types. These studies reveal a number of interactions, some of which are conserved across HPV types and others that are unique to a single HPV species or HPV genus. Binding of E7 to UBR4/p600 is conserved across all virus types, whereas the cellular protein ENC1 binds specifically to the E7s from HPV18 and HPV45, both members of genus alpha, species 7. We identify a specific interaction of HPV16 E7 with ZER1, a substrate specificity factor for a cullin 2 (CUL2)-RING ubiquitin ligase, and show that ZER1 is required for the binding of HPV16 E7 to CUL2. We further show that ZER1 is required for the destabilization of the retinoblastoma tumor suppressor RB1 in HPV16 E7-expressing cells and propose that a CUL2-ZER1 complex functions to target RB1 for degradation in HPV16 E7-expressing cells. These studies refine the current understanding of HPV E7 functions and establish a platform for the rapid identification of virus-host interactions.T he many types of human papillomaviruses (HPVs) that have been described exhibit considerable diversity. The HPVs are DNA viruses with a tropism specific for squamous epithelial cells. More than 120 HPVs have been identified and cloned to date, and these share a conserved genomic structure with eight to 10 ORFs encoded on one strand of a small double-stranded circular DNA genome (1). The ORFs involved in fundamental processes such as DNA replication or capsid formation are well conserved. Other ORFs, such as E6 and E7, have some conserved features but are more divergent at the nucleotide and protein level. Consistent with these differences, the lesions that are caused by infection with different HPVs and the propensity for these lesions to progress to cancer vary as well (2). A subset of the HPVs are the primary etiological agent in the development of cervical cancer, and other HPVs cause genital or cutaneous warts or other skin lesions. Relatively little is known about how these sequence differences translate into different biological outcomes in infected human cells. Thus, there exists an opportunity to systematically define features of diverse HPVs and to understand at the molecular level how their varied genetic compositions result in different disease states.The standard phylogeny of the HPVs is based on the sequence of the L1 gene, and a virus with an L1 DNA sequence that differs by 10% or more from other HPV L1s is designated as a separate type (1). Similar HPV types are grouped into species and further into genera. The majority of the HPVs identi...

1 Mast cells derive from the bone marrow and are responsible for the development of allergic and possibly in¯ammatory reactions. Mast cells are stimulated by immunoglobulin E (IgE) and speci®c antigen, but also by a number of neuropeptides such as neurotensin (NT), somatostatin or substance P (SP), to secrete numerous pro-in¯ammatory molecules that include histamine, cytokines and proteolytic enzymes. 2 Chondroitin sulphate, a major constituent of connective tissues and of mast cell secretory granules, had a dose-dependent inhibitory eect on rat peritoneal mast cell release of histamine induced by the mast cell secretagogue compound 48/80 (48/80). This inhibition was stronger than that of the clinically available mast cell`stabilizer' disodium cromoglycate (cromolyn). Inhibition by chondroitin sulphate increased with the length of preincubation and persisted after the drug was washed o, while the eect of cromolyn was limited by rapid tachyphylaxis. 3 Immunologic stimulation of histamine secretion from rat connective tissue mast cells (CTMC) was also inhibited, but this eect was weaker in umbilical cord-derived human mast cells and was absent in rat basophilic leukemia (RBL) cells which are considered homologous to mucosal mast cells (MMC). Oligo-and monosaccharides were not as eective as the polysaccharides. 4 Inhibition, documented by light and electron microscopy, involved a decrease of intracellular calcium ion levels shown by confocal microscopy and image analysis. Autoradiography at the ultrastructural level showed that chondroitin sulphate was mostly associated with plasma and perigranular membranes.5 Chondroitin sulphate appears to be a potent mast cell inhibitor of allergic and nonimmune stimulation with potential clinical implications.

Pentosanpolysulfate appears to be a potent inhibitor of allergic and nonimmune mast cell stimulation, which is an alternative explanation of its benefit in interstitial cystitis.

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