Related Experiment Video
Updated: Jul 14, 2026
07:02
An Assay for Quantifying Protein-RNA Binding in Bacteria
Published on: June 12, 2019
Human CCAAT-binding proteins have heterologous subunits
L A Chodosh1, A S Baldwin, R W Carthew
1Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
Cell
|April 8, 1988
Summary
Researchers identified three distinct CCAAT-binding proteins (CP1, CP2, and nuclear factor I) in HeLa cells. These proteins bind to specific DNA sequences and surprisingly function as multisubunit complexes.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The CCAAT sequence is a crucial regulatory element in eukaryotic promoters.
- Understanding CCAAT-binding proteins is essential for deciphering gene transcription regulation.
Purpose of the Study:
- To characterize distinct CCAAT-binding proteins in HeLa cell extracts.
- To investigate the binding specificities and complex formation of these proteins.
Main Methods:
- Protein purification from HeLa cell extracts.
- DNA-binding assays to determine binding affinities and specificities.
- Analysis of protein subunit composition.
Main Results:
- Identified three distinct CCAAT-binding proteins: CP1, CP2, and nuclear factor I (NF-I).
- CP1 binds to alpha-globin and adenovirus major late promoter (MLP) CCAAT elements.
- CP2 binds to the gamma-fibrinogen promoter CCAAT element.
- NF-I binds to the adenovirus replication origin.
- Each protein exhibits high specificity for its cognate binding site.
- CP1, CP2, and NF-I function as multisubunit complexes, with CP1 forming a stable complex from heterologous subunits.
Conclusions:
- CCAAT-binding proteins CP1, CP2, and NF-I are distinct molecular entities with specific DNA recognition.
- These proteins likely represent a family of related multisubunit complexes.
- The multisubunit nature is critical for their high-affinity DNA binding and function.
Related Concept Videos
02:41Protein Complex Assembly
Proteins can form homomeric complexes with another unit of the same protein or heteromeric complexes with different types. Most protein complexes self-assemble spontaneously via ordered pathways, while some proteins need assembly factors that guide their proper assembly. Despite the crowded intracellular environment, proteins usually interact with their correct partners and form functional complexes.
Many viruses self-assemble into a fully functional unit using the infected host cell to...
Many viruses self-assemble into a fully functional unit using the infected host cell to...
01:57Protein Complexes with Interchangeable Parts
Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
01:19Allosteric Proteins-ATCase
Binding sites linkages can regulate a protein's function. For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
01:57Protein Complexes with Interchangeable Parts
Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
01:25Structure of Cadherins
The cadherins were one of the first cell adhesion molecules discovered; the term “cadherins” is based on their calcium-dependent adhering properties. The first cadherins discovered on the epithelial, neuronal, and placental cells were named E-cadherin, P-cadherin, and N-cadherin, respectively. These classical cadherins share sequence and structural similarities. Other cadherins, including those involved in cell signaling, are grouped into non-classical cadherins. This diversity of cadherins...
01:23Catenins
Catenins are characterized by multiple binding domains and dynamic structures that allow them to function as linker proteins in cell junction complexes. All catenins, except α-catenin, contain a characteristic protein sequence called the armadillo repeat and are therefore also called armadillo proteins.
Catenins in Cell Junctions
Catenins bind to cell adhesion molecules such as cadherins and link them to different cytoskeletal proteins depending on the type of cell junction. At the adherens...
Catenins in Cell Junctions
Catenins bind to cell adhesion molecules such as cadherins and link them to different cytoskeletal proteins depending on the type of cell junction. At the adherens...