NONO regulates the intra-S-phase checkpoint in response to UV radiation.

The main risk factor for skin cancer is ultraviolet (UV) exposure, which causes DNA damage. Cells respond to UV-induced DNA damage by activating the intra-S-phase checkpoint, which prevents replication fork collapse, late origin firing and stabilizes fragile sites. Recently, the 54-kDa multifunctional protein NONO was found to be involved in the non-homologous end-joining DNA repair process and in poly ADP-ribose polymerase 1 activation. Interestingly, NONO is mutated in several tumour types and emerged as a crucial factor underlying both melanoma development and progression. Therefore, we set out to evaluate whether NONO could be involved in the DNA-damage response to UV radiations. We generated NONO-silenced HeLa cell clones and found that lack of NONO decreased cell growth rate. Then, we challenged NONO-silenced cells with exposure to UV radiations and found that NONO-silenced cells, compared with control cells, continued to synthesize DNA, failed to block new origin firing and impaired CHK1S345 phosphorylation showing a defective checkpoint activation. Consistently, NONO is present at the sites of UV-induced DNA damage where it localizes to RAD9 foci. To position NONO in the DNA-damage response cascade, we analysed the loading onto chromatin of various intra-S-phase checkpoint mediators and found that NONO favours the loading of topoisomerase II-binding protein 1 acting upstream of the ATM and Rad3-related kinase activity. Strikingly, re-expression of NONO, through an sh-resistant mRNA, rescued CHK1S345 phosphorylation in NONO-silenced cells. Interestingly, NONO silencing affected cell response to UV radiations also in a melanoma cell line. Overall, our data uncover a new role for NONO in mediating the cellular response to UV-induced DNA damage.

Surgical management of chronic, unreduced posterior dislocation of the shoulder.

Four patients with chronic posterior dislocation of the shoulder underwent surgical treatment after an average delay of 10 months from injury. They were examined clinically and radiographically at an average follow-up of 32 months. Treatment consisted of subscapularis tendon transfer (McLaughlin procedure) into the humeral defect in one case, transfer of the lesser tuberosity (McLaughlin modified procedure) in two cases, and in the fourth case-a patient with a 19-month missed dislocation and 50% humeral head lesion-a transposition of the coracoid process and conjoined tendon was performed. X-rays and CT scan excluded avascular necrosis or severe post-traumatic arthrosis. All patients achieved complete pain relief without limitation of daily or work activities. A slight limitation of anterior elevation and external rotation was present in all patients. Our results confirm that McLaughlin's original or modified procedure is suggested in cases of chronic, unreduced posterior dislocation of the shoulder (type I according to Randelli). The transposition of the coracoid process is a valid alternative to prosthesis and to autologous or homologous bone graft implants.

Tibial intercondylar eminence fractures in adults: arthroscopic treatment.

Results obtained from the surgical treatment of 15 cases of type II and III tibial intercondylar eminence fractures-according to the classification of Meyers and McKeever [12, 13]-are reported in this paper. The average age of the patients observed was 22 years (range 18-41). All patients underwent an arthroscopic procedure of reduction and fixation. We used a bioabsorbable suture in ten patients and a nonabsorbable suture in five patients. The suture was passed at the ACL insertion, then pulled out through drilled tunnels and tied onto the anterior surface of the tibial metaphysis. Two of the 15 patients treated underwent an additional arthroscopic procedure because of arthrofibrosis, 2 months after the first surgical intervention. All patients were examined clinically and radiographically with an average follow-up of 18 months. According to the IKDC scoring system, recovery of the 13 patients not undergoing additional intervention was graded as normal or near normal. In 14 patients, anterior laxity was inferior to 5 mm at the KT-1000 arthrometer evaluation. Absorbable or nonabsorbable suture fixation is effective for obtaining a secure fixation and achieves good clinical and functional mid-term results.

Results of autologous osteochondral grafts in chondral lesions of the knee.

BACKGROUND: To evaluate multiple osteochondral autografts for the treatment of traumatic chondral lesions of the knee. METHODS: Twenty-four (19 male and 5 female) patients underwent multiple osteochondral transplantation from 1995 to1999, the age ranging from 19 and 47 years old. Osteochondral lesion was localized on the femoral condyle in 21 cases, on the patella in 1 case and on the femoral groove in other 2 cases. The size of the lesion varied from 1 cm2 to 3 cm2. In 7 cases a single osteochondral graft and in 14 multiple ostechondral grafts has been harvested from non weight bearing areas of the knee. All patients except four were operated by arthroscopy. Four patients underwent arthrotomy because of the location of the lesion. The patients were examined with a 1 and 3 month follow-up and yearly thereafter (average f.u. 2 years and 4 months). For the clinical evaluation we used the IKDC Subjective Knee Evaluation Form. Before surgery, and, thereafter, during the follow-up sessions, the circumference of the thigh 10 cm proximally to the superior apex of the patella was measured. RESULTS: The results were evaluated as satisfactory in 75% of the cases (18/24). Best results were obtained in isolated chondral lesions and in cases that requested a smaller number of grafts. All the patients had an excellent recovery of the ROM, while a 1.3 cm side to side difference of muscle trophism (thigh circumference) was present during the one year follow-up. CONCLUSIONS: We report good results with multiple autologous osteochondral grafts. Multiple osteochondral grafts appears to be the "Golden standard", in the treatment of chondral lesions lesions between 1.5 and 3.5 cm2.

Tibial plateau fracture after arthroscopic anterior cruciate ligament reconstruction.

Complications have been described with each technique for reconstruction of the anterior cruciate ligament (ACL) in the knee, both open and arthroscopically assisted. The authors describe a case of tibial plateau fracture occurring 7 months after an ACL reconstruction using the half tunnel technique. The fracture occurred at the tibial fixation site and required open reduction with internal fixation. To our knowledge, only 2 cases of proximal tibial fracture after patellar tendon autograft ACL reconstruction have been previously reported. The authors hypothesize that patellar tendon harvesting with bone blocks and transosseous tibial tunnel can produce a "stress riser" effect and somehow act synergistically to create decreased strength at the level of proximal tibial metaphysis.

Cpc2, a fission yeast homologue of mammalian RACK1 protein, interacts with Ran1 (Pat1) kinase To regulate cell cycle progression and meiotic development.

The Schizosaccharomyces pombe ran1/pat1 gene regulates the transition between mitosis and meiosis. Inactivation of Ran1 (Pat1) kinase is necessary and sufficient for cells to exit the cell cycle and undergo meiosis. The yeast two-hybrid interaction trap was used to identify protein partners for Ran1/Pat1. Here we report the identification of one of these, Cpc2. Cpc2 encodes a homologue of RACK1, a WD protein with homology to the beta subunit of heterotrimeric G proteins. RACK1 is a highly conserved protein, although its function remains undefined. In mammalian cells, RACK1 physically associates with some signal transduction proteins, including Src and protein kinase C. Fission yeast cells containing a cpc2 null allele are viable but cell cycle delayed. cpc2Delta cells fail to accumulate in G(1) when starved of nitrogen. This leads to defects in conjugation and meiosis. Copurification studies show that although Cpc2 and Ran1 (Pat1) physically associate, Cpc2 does not alter Ran1 (Pat1) kinase activity in vitro. Using a Ran1 (Pat1) fusion to green fluorescent protein, we show that localization of the kinase is impaired in cpc2Delta cells. Thus, in parallel with the proposed role of RACK1 in mammalian cells, fission yeast cpc2 may function as an anchoring protein for Ran1 (Pat1) kinase. All defects associated with loss of cpc2 are reversed in cells expressing mammalian RACK1, demonstrating that the fission yeast and mammalian gene products are indeed functional homologues.