DNA damage-induced phosphorylation of CtIP at a conserved ATM/ATR site T855 promotes lymphomagenesis in mice.

CtIP is a DNA end resection factor widely implicated in alternative end-joining (A-EJ)-mediated translocations in cell-based reporter systems. To address the physiological role of CtIP, an essential gene, in translocation-mediated lymphomagenesis, we introduced the T855A mutation at murine CtIP to nonhomologous end-joining and Tp53 double-deficient mice that routinely succumbed to lymphomas carrying A-EJ-mediated IgH-Myc translocations. T855 of CtIP is phosphorylated by ATM or ATR kinases upon DNA damage to promote end resection.

Mouse Models of Germinal Center Derived B-Cell Lymphomas.

Over the last decades, the revolution in DNA sequencing has changed the way we understand the genetics and biology of B-cell lymphomas by uncovering a large number of recurrently mutated genes, whose aberrant function is likely to play an important role in the initiation and/or maintenance of these cancers. Dissecting how the involved genes contribute to the physiology and pathology of germinal center (GC) B cells -the origin of most B-cell lymphomas- will be key to advance our ability to diagnose and treat these patients. Genetically engineered mouse models (GEMM) that faithfully recapitulate lymphoma-associated genetic alterations offer a valuable platform to investigate the pathogenic roles of candidate oncogenes and tumor suppressors , and to pre-clinically develop new therapeutic principles in the context of an intact tumor immune microenvironment.

Unique and Shared Epigenetic Programs of the CREBBP and EP300 Acetyltransferases in Germinal Center B Cells Reveal Targetable Dependencies in Lymphoma.

Inactivating mutations of the CREBBP and EP300 acetyltransferases are among the most common genetic alterations in diffuse large B cell lymphoma (DLBCL) and follicular lymphoma (FL). Here, we examined the relationship between these two enzymes in germinal center (GC) B cells, the normal counterpart of FL and DLBCL, and in lymphomagenesis by using conditional GC-directed deletion mouse models targeting Crebbp or Ep300. We found that CREBBP and EP300 modulate common as well as distinct transcriptional programs implicated in separate anatomic and functional GC compartments.

The CREBBP Acetyltransferase Is a Haploinsufficient Tumor Suppressor in B-cell Lymphoma.

Inactivating mutations of the CREBBP acetyltransferase are highly frequent in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL), the two most common germinal center (GC)-derived cancers. However, the role of CREBBP inactivation in lymphomagenesis remains unclear. Here, we show that CREBBP regulates enhancer/super-enhancer networks with central roles in GC/post-GC cell fate decisions, including genes involved in signal transduction by the B-cell receptor and CD40 receptor, transcriptional control of GC and plasma cell development, and antigen presentation.