Functional relevance of novel p300-mediated lysine 314 and 315 acetylation of RelA/p65

Nuclear factor kappaB (NF-kappaB) plays an important role in the transcriptional regulation of genes involved in immunity and cell survival. We show here in vitro and in vivo acetylation of RelA/p65 by p300 on lysine 314 and 315, two novel acetylation sites. Additionally, we confirmed the acetylation on lysine 310 shown previously. Genetic complementation of RelA/p65-/- cells with wild type and non-acetylatable mutants of RelA/p65 (K314R and K315R) revealed that neither shuttling, DNA binding nor the induction of anti-apoptotic genes by tumor necrosis factor alpha was affected by acetylation on these residues. Microarray analysis of these cells treated with TNFalpha identified specific sets of genes differently regulated by wild type or acetylation-deficient mutants of RelA/p65. Specific genes were either stimulated or repressed by the acetylation-deficient mutants when compared to RelA/p65 wild type. These results support the hypothesis that site-specific p300-mediated acetylation of RelA/p65 regulates the specificity of NF-kappaB dependent gene expressio

Acetylation of p65 at lysine 314 is important for late NF-kappaB-dependent gene expression

Background: NF-κB regulates the expression of a large number of target genes involved in the immune and inflammatory response, apoptosis, cell proliferation, differentiation and survival. We have earlier reported that p65, a subunit of NF-κB, is acetylated in vitro and in vivo at three different lysines (K310, K314 and K315) by the histone acetyltransferase p300. Results: In this study, we describe that site-specific mutation of p65 at lysines 314 and 315 enhances gene expression of a subset of NF-κB target genes including Mmp10 and Mmp13. Increased gene expression was mainly observed three hours after TNFα stimulation. Chromatin immunoprecipitation (ChIP) experiments with an antibody raised against acetylated lysine 314 revealed that chromatin-bound p65 is indeed acetylated at lysine 314. Conclusions: Together, our results establish acetylation of K314 as an important regulatory modification of p65 and subsequently of NF-kappaB-dependent gene expression

CARM1 but not its enzymatic activity is required for transcriptional coactivation of NF-kappaB-dependent gene expression

Coactivator-associated arginine methyltransferase 1 (CARM1) belongs to the protein arginine methyltransferase family. It was reported to methylate histone as well as non-histone proteins and thus to be involved in transcriptional activation and mRNA degradation/stability. Here we report the genetic complementation of carm1-/- cells with wild-type CARM1 or an enzymatic inactive mutant of CARM1 to investigate the requirement of CARM1 and its enzymatic activity for nuclear factor kappaB (NF-kappaB)-dependent gene expression. Using custom microarray and quantitative reverse transcription PCR, we could define a subset of NF-kappaB target genes that required CARM1 for their proper expression. Although several tumor necrosis factor-alpha- and phorbol-12-myristate-13-acetate/ionomycin-induced NF-kappaB target genes are CARM1 dependent, CARM1 enzymatic activity was dispensable for gene expression. Interestingly, CARM1 was not required for the stimulus-dependent recruitment of RelA/p65 to chromatin, suggesting that CARM1 is rather contributing in protein complex stabilization. Together, our results confirm the importance of CARM1 as transcriptional cofactor without the involvement of its catalytic activity

Do all patients with advanced HER2 positive breast cancer need upfront-chemo when receiving trastuzumab? Randomized phase III trial SAKK 22/99.

HER2-targeted therapy plus chemotherapy is standard treatment in advanced HER2+ breast cancer. Trastuzumab alone followed by addition of chemotherapy at disease progression versus upfront combination therapy has not been elucidated. One-hundred seventy-five patients with measurable/evaluable HER2+ advanced disease without previous HER2-directed therapy were randomized to trastuzumab alone followed, at disease progression, by the combination with chemotherapy (Arm A) or upfront trastuzumab plus chemotherapy (Arm B). Chemotherapy could be stopped after ≥6 cycles in responding patients, trastuzumab was continued until progression. The primary endpoint of this superiority trial was time to progression (TTP) on combined trastuzumab-chemotherapy (Combination-TTP) in both arms. Secondary endpoints included response rate, TTP, overall survival, quality of life and toxicity. Combination-TTP was longer than expected in both arms, 12.2 months in Arm A and 10.3 months in Arm B and not significantly different (hazard ratio [HR] 0.7; 95% CI 0.5-1.1; P =0.1). Overall survival was also not significantly different (HR 0.9; 95% CI 0.6-1.5; P = 0.55). In Arm A, the median TTP before introduction of chemotherapy was 3.7 months (95% CI 2.3-5.4), yet at 2 years 6% of patients were still on trastuzumab alone. Patients without visceral disease had a Combination-TTP of 21.8 months in arm A, compared with 10.1 months in arm B (unplanned analysis HR 2.1, 95% CI 1.1-4.2, P = 0.03). Patients with visceral disease showed no difference. Toxicity was chemotherapy-related. The outcome of patients receiving sequential trastuzumab-chemotherapy or upfront combination was similar. We failed to demonstrate superiority of the sequential approach. These results nevertheless suggest chemotherapy and its toxicity can be deferred, especially in patients with indolent, non-visceral disease. Despite a larger non-inferiority confirmatory study would be needed, these findings represent an additional proof of concept that de-escalation strategies can be discussed in individual patients