The cell biology of mitochondrial membrane dynamics

Owing to their ability to efficiently generate ATP required to sustain normal cell function, mitochondria are often considered the \u2018powerhouses of the cell\u2019. However, our understanding of the role of mitochondria in cell biology recently expanded when we recognized that they are key platforms for a plethora of cell signalling cascades. This functional versatility is tightly coupled to constant reshaping of the cellular mitochondrial network in a series of processes, collectively referred to as mitochondrial membrane dynamics and involving organelle fusion and fission (division) as well as ultrastructural remodelling of the membrane. Accordingly, mitochondrial dynamics influence and often orchestrate not only metabolism but also complex cell signalling events, such as those involved in regulating cell pluripotency, division, differentiation, senescence and death. Reciprocally, mitochondrial membrane dynamics are extensively regulated by post-translational modifications of its machinery and by the formation of membrane contact sites between mitochondria and other organelles, both of which have the capacity to integrate inputs from various pathways. Here, we discuss mitochondrial membrane dynamics and their regulation and describe how bioenergetics and cellular signalling are linked to these dynamic changes of mitochondrial morphology

How do cytokines trigger genomic instability?

Inflammation is a double-edged sword presenting a dual effect on cancer development, from one hand promoting tumor initiation and progression and from the other hand protecting against cancer through immunosurveillance mechanisms. Cytokines are crucial components of inflammation, participating in the interaction between the cells of tumor microenvironment. A comprehensive study of the role of cytokines in the context of the inflammation-tumorigenesis interplay helps us to shed light in the pathogenesis of cancer. In this paper we focus on the role of cytokines in the development of genomic instability, an evolving hallmark of cancer. © 2012 Ioannis L. Aivaliotis et al

Author Correction: Mutational signatures reveal the role of RAD52 in p53-independent p21-driven genomic instability (Genome Biology, (2018), 19, 1, (37), 10.1186/s13059-018-1401-9)

Following publication of the original article [1], the authors identified an error in additional file 1. Two minor typing errors were discovered in legends S2 and S6. The updated additional file 1 is given in this correction article. © The Author(s) 2022

Mutational signatures reveal the role of RAD52 in p53-independent p21-driven genomic instability

Background: Genomic instability promotes evolution and heterogeneity of tumors. Unraveling its mechanistic basis is essential for the design of appropriate therapeutic strategies. In a previous study, we reported an unexpected oncogenic property of p21WAF1/Cip1, showing that its chronic expression in a p53-deficient environment causes genomic instability by deregulation of the replication licensing machinery. Results: We now demonstrate that p21WAF1/Cip1 can further fuel genomic instability by suppressing the repair capacity of low- and high-fidelity pathways that deal with nucleotide abnormalities. Consequently, fewer single nucleotide substitutions (SNSs) occur, while formation of highly deleterious DNA double-strand breaks (DSBs) is enhanced, crafting a characteristic mutational signature landscape. Guided by the mutational signatures formed, we find that the DSBs are repaired by Rad52-dependent break-induced replication (BIR) and single-strand annealing (SSA) repair pathways. Conversely, the error-free synthesis-dependent strand annealing (SDSA) repair route is deficient. Surprisingly, Rad52 is activated transcriptionally in an E2F1-dependent manner, rather than post-translationally as is common for DNA repair factor activation. Conclusions: Our results signify the importance of mutational signatures as guides to disclose the repair history leading to genomic instability. We unveil how chronic p21WAF1/Cip1 expression rewires the repair process and identifies Rad52 as a source of genomic instability and a candidate therapeutic target. © 2018 The Author(s)

Molecular patterns of response and treatment failure after frontline venetoclax combinations in older patients with AML

The BCL-2 inhibitor venetoclax combined with hypomethylating agents or low-dose cytarabine represents an important new therapy for older or unfit patients with acute myeloid leukemia (AML). We analyzed 81 patients receiving these venetoclax-based combinations to identify molecular correlates of durable remission, response followed by relapse (adaptive resistance) or refractory disease (primary resistance). High response rates and durable remissions were typically associated with NPM1 or IDH2 mutations (mut), with prolonged molecular remissions prevalent for NPM1mut. Primary and adaptive resistance to venetoclax-based combinations were most commonly characterized by acquisition or enrichment of clones activating signaling pathways such as FLT3 or RAS, or bi-allelically perturbing TP53. Single cell studies highlighted the polyclonal nature of intra-tumoral resistance mechanisms in some cases. Among cases that were primary refractory, we identified heterogeneous and sometimes divergent interval changes in leukemic clones within a single cycle of therapy, highlighting the dynamic and rapid occurrence of therapeutic selection in AML. In functional studies, FLT3-ITD gain or TP53 loss conferred cross-resistance to both venetoclax and cytotoxic-based therapies. Collectively, we highlight molecular determinants of outcome with clinical relevance to patients with AML receiving venetoclax-based combination therapies.C. D. DiNardo, I. S. Tiong, A. Quaglieri, S. MacRaild, S. Loghavi ... Ing Soo Tiong ... et al