Vitiligo is an acquired pigmentary disorder characterized by sharply demarcated, variably shaped depigmented macules and patches that appear commonly, but not exclusively, on the face, dorsa of the hands, nipples, axillae, umbilicus, and sacral, inguinal, and anogenital regions, surrounded by normal skin (Ezzedine, Eleftheriadou, Whitton, & Geel, 2015). Vitiligo can be broadly classified into two major forms, non-segmental and segmental vitiligo (Figure 1). This classification is based in part on the distinct prognosis and response to treatment between these two major types (
BackgroundThe purpose of the study was to compare the histopathologic and immunophenotypic features of central centrifugal cicatricial alopecia (CCCA) and lichen planopilaris (LPP) to better characterize and differentiate these two clinical entities. CCCA remains an ill‐defined and still‐unsettled histologic entity and many hair loss experts regard CCCA to be histologically indistinguishable from LPP. Given the overlapping histologic features of these two lymphocyte‐predominant cicatricial alopecias, and the lack of consensus regarding the significance of proposed distinctions, dermatopathologists face difficulty in providing clinicians and patients certainty with a definitive diagnosis of CCCA vs LPP.MethodsWe performed a retrospective review of 51 scalp biopsies of patients with either the clinical diagnosis of CCCA (27 cases) or LPP (24 cases). Clinical information, histologic features of hematoxylin‐eosin‐stained sections, and a panel of immunohistochemical markers were evaluated on scalp biopsies. Tested parameters were quantified, and statistical analysis was performed.ResultsOur study found no differences on either histologic assessment or immunophenotypic characterization between cases of classic LPP and CCCA.ConclusionThe conclusion of this study is that the inflammatory infiltrates in CCCA and LPP are not only histologically similar but also immunophenotypically indistinguishable.
Background: Helicase loading protein Gp59 coordinates recombination-dependent DNA replication in bacteriophage T4. Results: A DNA binding-deficient mutant, Gp59-I87A, loads helicase normally onto ssDNA covered with the ssDNA-binding protein, Gp32. Conclusion: Gp59-Gp32 interactions control helicase loading onto D-loops during recombination-dependent replication. Significance: Helicase loading proteins work in concert with single-stranded DNA binding proteins to control the location and timing of helicase assembly in DNA replication, recombination, and repair.
Dda, one of three helicases encoded by bacteriophage T4, has been well-characterized biochemically but its biological role remains unclear. It is thought to be involved in origin dependent DNA replication, recombination-dependent replication, anti-recombination, and recombination repair. The Gp32 protein of bacteriophage T4 plays critical roles in DNA replication, recombination, and repair by coordinating protein components of the replication fork and by stabilizing ssDNA. Previous work demonstrated that stimulation of DNA synthesis by Dda helicase appears to require direct Gp32-Dda protein-protein interactions and that Gp32 and Dda form a tight complex in the absence of ssDNA. Here we characterize the effects of Gp32-Dda physical and functional interactions through changes in the duplex DNA unwinding and ATPase activities of Dda helicase in the presence of different variants of Gp32 and different DNA repair and replication intermediate structures. Results show that Gp32-Dda interactions can be enhancing or inhibitory, depending on the Gp32 domain seen by Dda. Protein-protein interactions with Gp32 stimulate the unwinding activity of Dda, an effect associated with increased turnover of ATP, suggesting a higher rate of ATPase-driven translocation. Dda-Gp32 interactions also promote the unwinding of DNA substrates at higher salt concentrations and in the presence of substrate-bound DNA polymerase. Conversely, the formation of Gp32 clusters on ssDNA can inhibit unwinding, suggesting that Gp32-ssDNA formation sterically regulates which portions of replication and recombination intermediates are accessible for processing by Dda helicase. The data suggest a mechanism of replication fork restart in which Gp32 promotes Dda activity in template switching while preventing premature fork progression.
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