Investigation of the Acetylation Mechanism by GCN5 Histone Acetyltransferase

The histone acetylation of post-translational modification can be highly dynamic and play a crucial role in regulating cellular proliferation, survival, differentiation and motility. Of the enzymes that mediate post-translation modifications, the GCN5 of the histone acetyltransferase (HAT) proteins family that add acetyl groups to target lysine residues within histones, has been most extensively studied. According to the mechanism studies of GCN5 related proteins, two key processes, deprotonation and acetylation, must be involved. However, as a fundamental issue, the structure of hGCN5/AcCoA/pH3 remains elusive. Although biological experiments have proved that GCN5 mediates the acetylation process through the sequential mechanism pathway, a dynamic view of the catalytic process and the molecular basis for hGCN5/AcCoA/pH3 are still not available and none of theoretical studies has been reported to other related enzymes in HAT family. To explore the molecular basis for the catalytic mechanism, computational approaches including molecular modeling, molecular dynamic (MD) simulation and quantum mechanics/molecular mechanics (QM/MM) simulation were carried out. The initial hGCN5/AcCoA/pH3 complex structure was modeled and a reasonable snapshot was extracted from the trajectory of a 20 ns MD simulation, with considering post-MD analysis and reported experimental results. Those residues playing crucial roles in binding affinity and acetylation reaction were comprehensively investigated. It demonstrated Glu80 acted as the general base for deprotonation of Lys171 from H3. Furthermore, the two-dimensional QM/MM potential energy surface was employed to study the sequential pathway acetylation mechanism. Energy barriers of addition-elimination reaction in acetylation obtained from QM/MM calculation indicated the point of the intermediate ternary complex. Our study may provide insights into the detailed mechanism for acetylation reaction of GCN5, and has important implications for the discovery of regulators against GCN5 enzymes and related HAT family enzymes

Intussusception in Childhood Acute T Cell Lymphoblastic Leukemia: An Unusual Complication - Report of 2 Cases.

Abstract Clinically significant gastrointestinal complications in children with acute lymphoblastic leukemia (ALL) have been reported. However, intussusception is a very rare complication. In one study of 286 children with ALL gastrointestinal complications occurred in 5.6% of patients with intussusception seen in only 0.3% of patients. We describe two cases of intussusception during chemotherapy for T-cell leukemia. Patient #1 was an 8 year old girl on chemotherapy for T-cell ALL. Around week 9 following POG 9404 protocol of consolidation chemotherapy, patient presented with severe abdominal pain and vomiting, and had marked, diffuse tenderness of the abdomen with guarding and hypo-active bowel sounds. Abdominal radiograph showed thickening of the descending colon; abdominal sonogram was normal; abdominal computed tomography (CT) scan however, revealed a soft tissue and fluid-filled mass extending from the cecum to the descending colon. These findings were consistent with a large bowel intussusception, which was successfully reduced with a barium enema. Patient #2 was a 15 year old male receiving chemotherapy for T-cell ALL following POG 9404 protocol. At week 14 of consolidation chemotherapy, patient presented with a 2 day history of nausea and colicky peri-umbilical and right lower quadrant abdominal pain. An abdominal CT scan revealed an ileocolic intussusception without bowel obstruction and mild wall thickening of the cecum. Barium enema resulted in successful reduction of the intussusception. Interestingly, both our patients were treated with high dose methotrexate 5gm/m2 during this time period and both experienced delayed excretion of methotrexate. To our knowledge, there is no known reported association between high dose methotrexate and intussusception. We speculate that the two could be related. The increased use of high dose methotrexate therapy in T-cell ALL may result in a higher incidence of intussusception in this population. Although, intussusception in ALL is a very rare complication, awareness of this entity and early recognition with radiological intervention may prevent unnecessary surgery and the associated morbidity and mortality in these patients.</jats:p

Nursing Facility (NF) Residents with Anemia Associated with Chronic Kidney Disease (CKD) Require Greater Assistance in Performing Activities of Daily Living (ADL) Compared to Residents with CKD without Anemia.

Abstract Anemia is a well known complication of CKD and is associated with symptoms of fatigue, decreased muscle strength, and reduced oxygen capacity. However, the effect of anemia associated with CKD on ADLs in NF residents has not been well described. The purpose of this analysis was to evaluate the effect of the anemia associated with CKD on ADLs in NF residents. ALTER (Anemia and associated outcomes in Long-TErm care Residents) was a retrospective study conducted in a representative sample of 24 NFs. Chart data was integrated with electronic Minimum Data Set (MDS) records and prescription claims for the 1-year period before the date of data abstraction. Eligible residents were ≥ 65 years, not receiving dialysis, and not comatose. CKD was conservatively defined as eGFR &lt; 60mL/min/1.73 m2 (MDRD equation). Anemia was defined by the WHO criteria (&lt; 13g/dL for men and &lt; 12g/dL for women). Residents were stratified into two groups: those with CKD and anemia and those with CKD but had no anemia. The first available record to estimate GFR was used to establish the presence of CKD. Diagnosis of anemia was established by an indication of anemia in the chart records as well as a laboratory diagnosis of anemia within 15 days of the chart record. Residents who did not have anemia had no records of an anemia diagnosis either in their chart or as a laboratory diagnosis. Section G of the MDS was used to describe ADLs. ADL scores of 0 or 1 were described as residents who needed slight help in performing an activity, and scores of 2, 3, or 4 were described as residents who needed moderate/significant help. Residents who did not perform an activity during a 7 day period were excluded (ADL score of 8). Bootstrapping, a statistical method which allows for the estimation of population parameters in order to draw inferences about the population(s) from which the data came, was applied to analyze the association of ADLs with CKD and anemia. From a database of 2204 residents, 1501 had a GFR record for CKD diagnosis. Of the 1501, 4.6% (69/1501) had CKD and a confirmed indication of anemia, and 6.9% (104/1501) had CKD but no anemia. The association between ADLs and disease are shown below. The results indicate that a greater percent of residents with CKD and anemia than residents with CKD but no anemia require moderate to significant assistance for their daily physical functioning and suggests that treating anemia may improve ADLs. Percent of residents requiring moderate to significant help (bootstrap 95% CI) ADL CKD, anemic (n=69) CKD, no anemia (n=104) Bed Mobility 78% (72%, 83%) 57% (52%, 62%) Transfer 83% (79%, 88%) 62% (58%, 67%) Walk in Room 71% (61%, 79%) 44% (38%, 51%) Walk in Corridor 70% (61%, 79%) 44% (37%, 51% Locomotion on Unit 72% (67%, 78%) 57% (51%, 62%) Locomotion off Unit 73% (67%, 79%) 64% (60%, 69%) Dressing 89% (86%, 93%) 79% (75%, 83%) Eating 25% (20%, 32%) 23% (20%, 27%) Toilet Use 84% (80%, 88%) 71% (67%, 74%) Personal Hygiene 84% (81%, 91%) 75% (72%, 79%)</jats:p