We previously showed that mRNA 3 0 end cleavage reaction in cell extracts is strongly but transiently inhibited under DNA-damaging conditions. The cleavage stimulation factor-50 (CstF-50) has a role in this response, providing a link between transcription-coupled RNA processing and DNA repair. In this study, we show that CstF-50 interacts with nuclear poly(A)-specific ribonuclease (PARN) using in vitro and in extracts of UV-exposed cells. The CstF-50/ PARN complex formation has a role in the inhibition of 3 0 cleavage and activation of deadenylation upon DNA damage. Extending these results, we found that the tumour suppressor BARD1, which is involved in the UV-induced inhibition of 3 0 cleavage, strongly activates deadenylation by PARN in the presence of CstF-50, and that CstF-50/ BARD1 can revert the cap-binding protein-80 (CBP80)-mediated inhibition of PARN activity. We also provide evidence that PARN along with the CstF/BARD1 complex participates in the regulation of endogenous transcripts under DNA-damaging conditions. We speculate that the interplay between polyadenylation, deadenylation and tumour-suppressor factors might prevent the expression of prematurely terminated messengers, contributing to control of gene expression under different cellular conditions.

Recent findings suggest that bone marrow-derived cells (BMDC) may contribute to tissue maintenance throughout the body. However, it is not yet known whether marrow-derived epithelial cells are capable of undergoing proliferation. Our laboratory has shown that BMDC engraft as keratinocytes in the skin at low levels (< 1%) in the absence of injury. Here we show that skin damage affects the degree of engraftment of BMDC as keratinocytes and that the keratinocytes are actively cycling. Female mice reconstituted with sex-mismatched BM were wounded by punch biopsy and incision. At the wound site, engraftment of BMDC as epidermal cells increased within 1 day, and continued to increase to approximately 4% by 3 weeks after injury. Using a Cre-lox system, fusion of BMDC with epithelial cells was ruled out. BMDC-derived epithelial cells at the wound edges expressed Ki67, a marker for actively cycling cells, and this proliferation correlated with an increase in the number of donor-derived cells within the wound. Donorderived cytokeratin 5-expressing cells were rare, suggesting that BMDC do not engraft as epidermal stem cells, and the level of engraftment peaked and then decreased over time, further suggesting that BMDC may assist in early wound healing by engrafting as transit-amplifying cells, which then differentiate into keratinocytes. We have shown that, in the absence of injury, bone marrow-derived cells (BMDC) engraft at low levels as epithelial cells in the liver, lung, GI tract, and skin. It is not yet clear whether this phenomenon is due to transdifferentiation of a hematopoietic stem cell, or whether the marrow contains pluripotent pre-hematopoietic cells thathave not yet initiated a gene expression pattern that commits them to either a hematopoietic or an epithelial fate (reviewed in 1 ). According to recent studies, BMDC show an increased contribution to tissues under pathological conditions. Following acute myocardial infarction, BMDC engraft as multiple cell types that promote survival/regeneration of heart tissue.2,3 A more pronounced effect is seen in a mouse model of tyrosinemia, where fusion of BMDC with diseased cells results in the formation of functional hepatocytes and restores liver function. 4 These findings led us to investigate whether cutaneous injury leads to increased engraftment of BMDC as epidermal cells.To allow for tracking of the BMDC, we reconstituted lethally irradiated mice with sex-mismatched BM. Following engraftment, we wounded the skin with full-thickness punch biopsies and incisional wounds, each of which heals by secondary intention. Analysis of the healing skin at different times showed that engraftment of BMDC as epidermal cells in the wounded area was significantly greater than in unwounded skin over the same time interval. The marrow-derived epithelial cells just beyond the wound edges were undergoing proliferation. Fusion was ruled out using the loxP-Cre system. Based on the pattern of engraftment over time, a conceptual model of this engraftment is proposed. Materials and Met...

Endoneurial laminins (Lms), β1-integrins, and dystroglycan (DG) are important for Schwann cell (SC) ensheathment and myelination of axons. We now show that SC expression of galactosyl-sulfatide, a Lm-binding glycolipid, precedes that of Lms in developing nerves. This glycolipid anchors Lm-1 and -2 to SC surfaces by binding to their LG domains and enables basement membrane (BM) assembly. Revealingly, non–BM-forming fibroblasts become competent for BM assembly when sulfatides are intercalated into their cell surfaces. Assembly is characterized by coalescence of sulfatide, DG, and c-Src into a Lm-associated complex; by DG-dependent recruitment of utrophin and Src activation; and by integrin-dependent focal adhesion kinase phosphorylation. Collectively, our findings suggest that sulfated glycolipids are key Lm anchors that determine which cell surfaces can assemble Lms to initiate BM assembly and DG- and integrin-mediated signaling.

Current GPUs are massively parallel multicore processors optimised for workloads with a large degree of SIMD parallelism. Good performance requires highly idiomatic programs, whose development is work intensive and requires expert knowledge.To raise the level of abstraction, we propose a domain-specific high-level language of array computations that captures appropriate idioms in the form of collective array operations. We embed this purely functional array language in Haskell with an online code generator for NVIDIA's CUDA GPGPU programming environment. We regard the embedded language's collective array operations as algorithmic skeletons; our code generator instantiates CUDA implementations of those skeletons to execute embedded array programs.This paper outlines our embedding in Haskell, details the design and implementation of the dynamic code generator, and reports on initial benchmark results. These results suggest that we can compete with moderately optimised native CUDA code, while enabling much simpler source programs.