Profilin regulates the activity of p42POP, a novel Myb-related transcription factor

Abstract

Profilins, regulators of cytoplasmic actin dynamics, also bind to several nuclear proteins but the significance of these interactions is mostly unclear. Here, we describe a novel Myb-related transcription factor, p42POP, as a new ligand for profilin and show that profilin regulates its activity. p42POP comprises a unique combination of domains and is widely expressed in mouse tissues. In contrast to many other Myb proteins, it contains only one functional tryptophan-cluster motif. This is followed by an acidic domain, a leucine zipper that mediates dimerization and functional nuclear import and export signals that can direct p42POP to either the nuclear or the cytoplasmic compartment. Binding to profilins is mediated by a proline-rich cluster. p42POP-profilin complexes can be precipitated from cell lysates. In transfected cells displaying p42POP in the nucleus, nuclear profilin is markedly increased. When p42POP is anchored at mitochondrial membranes, profilin is targeted to this location. Hence, in a cellular environment, p42POP and profilin are found in the same protein complex. In luciferase assays, p42POP acts as repressor and this activity is substantially reduced by profilins, indicating that profilin can regulate p42POP activity and is therefore involved in gene regulation.

The Interaction of Proline-Rich Ligands with Profilin Probed with an Enzyme-Linked Immunosorbent Assay

“…this method is, however, time-consuming and produces many false positives, and few poly(l-proline)-containing partners have been identified. 16,17 the interaction elISA presented here is fast, and the negative controls remained at low background levels. It has to be noted that in some cases where a relatively high background is measured (e.g., when using GSt fusion proteins), the use of a different fusion protein and/ or antibodies is recommended.…”

Silencing profilin-1 inhibits endothelial cell proliferation, migration and cord morphogenesis

“…1D). Since Pfn1 has been recently implicated in gene transcription (Lederer et al, 2005), we next asked whether expression levels of actin and some of the ABPs that are important for actin assembly in response to growth factor signaling such as VASP, N-WASP and mDia1 are altered as a result of silencing Pfn1. Immunoblots of whole cell lysates showed no appreciable change in the expression levels of actin and the indicated ABPs at any time-point after transfection (Fig.…”

Molecular insights on context-specific role of profilin-1 in cell migration

“…In the cytoplasmic compartment, Pfn1 interacts with important regulators of actin dynamics and organization [N-WASP (neural Wiskott-Aldrich syndrome protein), WAVE (WASP-associated verprolin homology protein), Diaphanous, Mena (mammalian enabled)/VASP/Evl (enabled/VASP like), palladin, RIAM (Rap1 GTP-interacting adaptor molecule)/lamellipodin], [30][31][32][33][34][35][36] cell-cell adhesion (AF-6), 37 and membrane trafficking [VCP (valocin containing protein), clathrin, huntingtin]. 38,39 Nuclear ligands of Pfn1 identified thus far include p42-POP (a myb-family transcription factor), 40 SMN (survival motor neuron proteininvolved in small ribonucleoprotein processing and transport) 41 and exportin-6 (involved in nuclear export of actin). 42 Functional diversity of these PLP ligands places Pfn1 at the crossroads of many physiological activities in cells ranging from actin cytoskeletal organization to gene transcription.…”