BRMS151–98 and BRMS151–84 Are Crystal Oligomeric Coiled Coils with Different Oligomerization States, Which Behave as Disordered Protein Fragments in Solution

Abstract

The breast cancer metastasis suppressor 1 (BRMS1) gene suppresses metastasis without affecting the primary tumor growth. Cellular localization of BRMS1 appears to be important for exerting its effects on metastasis inhibition. We recently described a nucleo-cytoplasmic shuttling for BRMS1 and identified a nuclear export signal within the N-terminal coiled coil. The structure of these regions shows an antiparallel coiled coil capable of oligomerizing, which compromises the accessibility to the nuclear export signal consensus residues. We have studied the structural and biophysical features of this region to further understand the contribution of the N-terminal coiled coil to the biological function of BRMS1. We have observed that residues 85 to 98 might be important in defining the oligomerization state of the BRMS1 N-terminal coiled coil. The fragments are mainly disordered in solution, with evidence of residual structure. In addition, we report the presence of a conformational dynamic equilibrium (oligomeric folded species ↔ oligomeric unfolded) in solution in the BRMS1 N-terminal coiled coil that might facilitate the nuclear export of BRMS1 to the cytoplasm.

Mcm10 Self-Association Is Mediated by an N-Terminal Coiled-Coil Domain

“…In fact, the crystal structure of the human T cell leukemia virus type 1 transmembrane ectodomain, determined as an MBP fusion, formed a parallel trimeric CC required for proper function [67], [68], further validating the importance of our trimeric MBP-Mcm10-CC structure. In addition, CC folding and remodeling in response to other environmental factors, including temperature and effector molecules is a general phenomenon [69], [70], [71], [72], [73], [74], [75]. On the basis of these examples and consistent with our data, we speculate that the Mcm10 CC exists mainly as an intrinsically disordered monomer or as a CC dimer, and has the propensity to attain other multimeric configurations in response to its environment.…”

The isolated C-terminal nuclear localization sequence of the breast cancer metastasis suppressor 1 is disordered

“…Based on our results in TFE, since NLS2 of BRMS1 does not undergo a disorder-to-order transition in the presence of a higher hydrophobic environment, we speculate that this specific NLS could not acquire a structure in the presence of any canonical binding partner of BRMS1. The unfolded nature of NLS2 may facilitate acquisition of versatile conformations to bind the multiple targets of BRMS1 (even those proteins not included in the nuclear envelope); such an intrinsically disordered state was also observed in solution for the isolated nuclear export signal of BRMS1 [11,12], although this region shows an inherent tendency to self-associate.…”

“…As a member of the family of metastasis suppressors, BRMS1 plays an active role in blocking tumour progression. This protein has several regions or domains [8,11], and for some of which their structures have been solved [11,12]. In this work we have focused on characterizing the conformation of the second NLS, at the C-terminal region of BMRS1, which is necessary for metastasis suppression [15].…”

“…Furthermore, BRMS1 acts at the levels of cell-cell communication and abrogation of phosphoinositide signalling [4,6], probably forming complexes with proteins involved in the regulation of transcription [4,[7][8][9], specifically with chromatin remodelling complexes [4,10]. Despite its wide biomedical interest, molecular characterization of BRMS1, including structural studies, remains largely elusive, and only recently the X-ray structure of the region comprising its nuclear export signal has been solved [11,12]. In solution, this region appears to be disordered, whereas in the crystal, it forms an oligomeric coiled-coil.…”

Structural insights into the assembly of the histone deacetylase-associated Sin3L/Rpd3L corepressor complex

“…Although the BRMS1 protein plays important roles in metastasis suppression of a variety of cancers (34), the precise molecular role of this protein in the context of the Sin3L/Rpd3L complex has been elusive. Structures of BRMS1 CC1 motif have provided contrasting views of higher-order association, with one segment of the protein crystallizing as a hexamer, a slightly different segment crystallizing as a dimer, and each association using distinct surfaces (35,36). We propose that a model for BRMS1 dimerization based on the structure of the Sds3 dimerization domain is likely to be physiologically relevant.…”