Related Experiment Video

Updated: Aug 7, 2026

Heterokaryon Technique for Analysis of Cell Type-specific Localization
09:31

Heterokaryon Technique for Analysis of Cell Type-specific Localization

Published on: March 11, 2011

Mechanisms directing the nuclear localization of the CtBP family proteins

Alexis Verger1, Kate G R Quinlan, Linda A Crofts

  • 1School of Molecular and Microbial Biosciences, Biochemistry Building G08, University of Sydney, Sydney, New South Wales 2006, Australia.

Molecular and Cellular Biology
|June 20, 2006
PubMed

Insights

The C-terminal binding protein (CtBP) family

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Protein Interactions

Background:

  • The C-terminal binding protein (CtBP) family comprises four proteins involved in transcriptional repression and intracellular trafficking.
  • Mechanisms controlling the subcellular localization of distinct CtBP proteins are not well understood.

Purpose of the Study:

  • To elucidate the differential regulation of nuclear import for CtBP proteins and splice isoforms.
  • To investigate the role of CtBP2 in nuclear localization and protein interactions.

Main Methods:

  • Heterokaryon assays were employed to study protein shuttling.
  • Analysis of nuclear localization signals (NLS) and protein-protein interactions (heterodimerization).
  • Investigated the impact of NADH binding site mutations on CtBP function.

Main Results:

  • CtBP2 possesses a unique N-terminal nuclear localization signal (NLS) facilitating nuclear accumulation and nucleocytoplasmic shuttling.
  • CtBP2 can heterodimerize with CtBP1 isoforms, directing them to the nucleus, dependent on the CtBP2 NLS.
  • A CtBP2 splice isoform (CtBP2-S) lacking the NLS localizes to the cytoplasm.
  • Binding to PXDLS motif transcription factors like BKLF also mediates nuclear import.
  • NADH binding site mutations disrupt dimerization, BKLF association, and CtBP1 nuclear accumulation.

Conclusions:

  • CtBP protein nuclear localization is regulated by the CtBP2 NLS, interactions with PXDLS motif proteins, and NADH-dependent dimerization.
  • Differential localization of CtBP family members is achieved through distinct regulatory mechanisms.

More Related Videos

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay12:26

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay

Published on: May 3, 2018

Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins05:35

Immunofluorescence Analysis of Endogenous and Exogenous Centromere-kinetochore Proteins

Published on: March 3, 2016

Related Concept Videos

Nuclear Protein Sorting01:34

Nuclear Protein Sorting

Nuclear protein sorting is the selective trafficking of histones, polymerases, gene regulatory proteins into the nucleus and exporting RNAs and ribosomes to the cytosol. It is a tightly controlled process that regulates gene expression within a cell.
Proteins targeted to the nucleus carry nuclear localization signals or NLS recognized by import receptors in the cytosol. Similarly, proteins with nuclear export signals are recognized by export receptors. Import and export receptors are...
Regulation of Nuclear Protein Sorting01:45

Regulation of Nuclear Protein Sorting

Nuclear protein sorting regulates nucleus composition and gene expression, crucial for determining the fate of a eukaryotic cell. Hence, the entry and exit of molecules across the nuclear envelope is a tightly controlled process. Nuclear protein sorting can be inhibited by one of the following ways: 1) masking cargo signal sequences, 2) modifying the nuclear receptor's affinity for cargo, 3) controlling the nuclear pore size, 4) retaining the cargo during its transit to the cytosol or the...
Nuclear Localization Signals and Import01:46

Nuclear Localization Signals and Import

Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of  2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
Nuclear Export01:42

Nuclear Export

The nucleus restricts several proteins within and allows others to pass. The restricted proteins possess a nuclear retention sequence or NRS, anchoring them to the nuclear lamins and preventing their transport to the cytosol. The non-restricted proteins, after their synthesis, are transported to their site of action, such as the cytosol or other organelles, with the help of nuclear export signals or NES.
NES are of three types- the canonical 10-residue long leucine-rich signal and other...
Directionality of Nuclear Transport01:42

Directionality of Nuclear Transport

Ras-related nuclear protein or Ran is a small G protein that cycles between its GTP and GDP bound states. Ran specific regulators, a Ran GTPase Activating Protein or RanGAP present in the cytosol and a Ran guanine nucleotide exchange factor or RanGEF present inside the nucleus regulate GTP/GDP exchange. A high concentration of GTP inside the cells, in addition to this asymmetric distribution of  Ran-specific regulators, leads to a higher RanGTP concentration inside the nucleus. This...
Regulated mRNA Transport02:22

Regulated mRNA Transport

In eukaryotes, transcription and translation are compartmentalized; an mRNA is first synthesized in the nucleus and then selectively transported to the cytoplasm for protein synthesis. Before transport, a pre-mRNA undergoes several steps of post-transcriptional modifications including splicing, 5' capping, and the addition of a poly-adenine tail. Various proteins bind to the pre-mRNA during these modifications. The mRNA transport takes place with the help of multiple proteins playing specific...