Calpain 2 activation of P-TEFb drives megakaryocyte morphogenesis and is disrupted by leukemogenic GATA1 mutation

Kamaleldin E Elagib; Jeremy D Rubinstein; Lorrie L Delehanty; Valerie S Ngoh; Peter A Greer; Shuran Li; Jae K Lee; Zhe Li; Stuart H Orkin; Ivailo S Mihaylov; Adam N Goldfarb

doi:10.1016/j.devcel.2013.11.013

Calpain 2 activation of P-TEFb drives megakaryocyte morphogenesis and is disrupted by leukemogenic GATA1 mutation

Dev Cell. 2013 Dec 23;27(6):607-20. doi: 10.1016/j.devcel.2013.11.013.

Authors

Affiliations

¹ Department of Pathology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
² Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada.
³ Department of Public Health Sciences, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
⁴ Division of Hematology/Oncology, Children's Hospital Boston, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA 02115, USA.
⁵ Department of Pathology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Electronic address: ang3x@virginia.edu.

Abstract

Megakaryocyte morphogenesis employs a "hypertrophy-like" developmental program that is dependent on P-TEFb kinase activation and cytoskeletal remodeling. P-TEFb activation classically occurs by a feedback-regulated process of signal-induced, reversible release of active Cdk9-cyclin T modules from large, inactive 7SK small nuclear ribonucleoprotein particle (snRNP) complexes. Here, we have identified an alternative pathway of irreversible P-TEFb activation in megakaryopoiesis that is mediated by dissolution of the 7SK snRNP complex. In this pathway, calpain 2 cleavage of the core 7SK snRNP component MePCE promoted P-TEFb release and consequent upregulation of a cohort of cytoskeleton remodeling factors, including α-actinin-1. In a subset of human megakaryocytic leukemias, the transcription factor GATA1 undergoes truncating mutation (GATA1s). Here, we linked the GATA1s mutation to defects in megakaryocytic upregulation of calpain 2 and of P-TEFb-dependent cytoskeletal remodeling factors. Restoring calpain 2 expression in GATA1s mutant megakaryocytes rescued normal development, implicating this morphogenetic pathway as a target in human leukemogenesis.

Publication types

Research Support, N.I.H., Extramural

MeSH terms

Actinin / genetics
Actinin / metabolism
Animals
Blotting, Western
Calpain / physiology*
Cell Differentiation
Cell Nucleus / genetics
Cell Nucleus / metabolism
Cell Proliferation
Cell Transformation, Neoplastic / metabolism
Cell Transformation, Neoplastic / pathology*
Cells, Cultured
Cytoskeleton / metabolism
Flow Cytometry
GATA1 Transcription Factor / genetics*
GATA1 Transcription Factor / metabolism
Humans
Immunoprecipitation
Leukemia / metabolism
Leukemia / pathology*
Megakaryocytes / metabolism
Megakaryocytes / pathology*
Mice
Mice, Inbred C57BL
Mice, Knockout
Mice, Transgenic
Morphogenesis
Mutation / genetics*
Positive Transcriptional Elongation Factor B / genetics
Positive Transcriptional Elongation Factor B / metabolism*
Protein Binding
RNA, Messenger / genetics
Real-Time Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction
Ribonucleoproteins, Small Nuclear / genetics
Ribonucleoproteins, Small Nuclear / metabolism*
Transcription, Genetic

Substances

GATA1 Transcription Factor
RNA, Messenger
Ribonucleoproteins, Small Nuclear
Actinin
Positive Transcriptional Elongation Factor B
Calpain
Capn1 protein, mouse

Abstract

Publication types

MeSH terms

Substances

Grants and funding