Biophysical characterization and modeling of human Ecdysoneless (ECD) protein supports a scaffolding function

Riyaz A. Mir; Jeff Lovelace; Nicholas P. Schafer; Peter D. Simone; Admir Kellezi; Carol Kolar; Gaelle Spagnol; Paul L. Sorgen; Hamid Band; Vimla Band; Gloria E. O. Borgstahl; Riyaz A. Mir; Jeff Lovelace; Nicholas P. Schafer; Peter D. Simone; Admir Kellezi; Carol Kolar; Gaelle Spagnol; Paul L. Sorgen; Hamid Band; Vimla Band; Gloria E. O. Borgstahl

doi:10.3934/biophy.2016.1.195

AIMS Biophysics

2016, Volume 3, Issue 1: 195-210. doi: 10.3934/biophy.2016.1.195

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Biophysical characterization and modeling of human Ecdysoneless (ECD) protein supports a scaffolding function

1.
Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
2.
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE 68198, USA
3.
Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
4.
Department of Biochemistry & Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA

Received: 09 December 2015 Accepted: 06 March 2016 Published: 09 March 2016

The human homolog of Drosophila ecdysoneless protein (ECD) is a p53 binding protein that stabilizes and enhances p53 functions. Homozygous deletion of mouse Ecd is early embryonic lethal and Ecd deletion delays G₁-S cell cycle progression. Importantly, ECD directly interacts with the Rb tumor suppressor and competes with the E2F transcription factor for binding to Rb. Further studies demonstrated ECD is overexpressed in breast and pancreatic cancers and its overexpression correlates with poor patient survival. ECD overexpression together with Ras induces cellular transformation through upregulation of autophagy. Recently we demonstrated that CK2 mediated phosphorylation of ECD and interaction with R2TP complex are important for its cell cycle regulatory function. Considering that ECD is a component of multiprotein complexes and its crystal structure is unknown, we characterized ECD structure by circular dichroism measurements and sequence analysis software. These analyses suggest that the majority of ECD is composed of α-helices. Furthermore, small angle X-ray scattering (SAXS) analysis showed that deletion fragments, ECD(1–432) and ECD(1–534), are both well-folded and reveals that the first 400 residues are globular and the next 100 residues are in an extended cylindrical structure. Taking all these results together, we speculate that ECD acts like a structural hub or scaffolding protein in its association with its protein partners. In the future, the hypothetical model presented here for ECD will need to be tested experimentally.
- Ecdysoneless,
- circular dichroism,
- SAXS,
- molecular modeling,
- structural hub,
- scaffold protein
Citation: Riyaz A. Mir, Jeff Lovelace, Nicholas P. Schafer, Peter D. Simone, Admir Kellezi, Carol Kolar, Gaelle Spagnol, Paul L. Sorgen, Hamid Band, Vimla Band, Gloria E. O. Borgstahl. Biophysical characterization and modeling of human Ecdysoneless (ECD) protein supports a scaffolding function[J]. AIMS Biophysics, 2016, 3(1): 195-210. doi: 10.3934/biophy.2016.1.195

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Abstract

The human homolog of Drosophila ecdysoneless protein (ECD) is a p53 binding protein that stabilizes and enhances p53 functions. Homozygous deletion of mouse Ecd is early embryonic lethal and Ecd deletion delays G₁-S cell cycle progression. Importantly, ECD directly interacts with the Rb tumor suppressor and competes with the E2F transcription factor for binding to Rb. Further studies demonstrated ECD is overexpressed in breast and pancreatic cancers and its overexpression correlates with poor patient survival. ECD overexpression together with Ras induces cellular transformation through upregulation of autophagy. Recently we demonstrated that CK2 mediated phosphorylation of ECD and interaction with R2TP complex are important for its cell cycle regulatory function. Considering that ECD is a component of multiprotein complexes and its crystal structure is unknown, we characterized ECD structure by circular dichroism measurements and sequence analysis software. These analyses suggest that the majority of ECD is composed of α-helices. Furthermore, small angle X-ray scattering (SAXS) analysis showed that deletion fragments, ECD(1–432) and ECD(1–534), are both well-folded and reveals that the first 400 residues are globular and the next 100 residues are in an extended cylindrical structure. Taking all these results together, we speculate that ECD acts like a structural hub or scaffolding protein in its association with its protein partners. In the future, the hypothetical model presented here for ECD will need to be tested experimentally.

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