# Binding Behavior of Human Hepatoma-Derived Growth Factor on SMYD1

## TL;DR

This study explores how parts of the HDGF protein bind to DNA and affect its fluorescence, revealing insights into cancer-related protein interactions.

## Contribution

The study identifies the binding behavior of HDGF and its domains on SMYD1 DNA using fluorescence quenching.

## Key findings

- HDGF and its domains cause fluorescence quenching when binding to Cy3-labeled SMYD1 DNA.
- The PWWP domain has about 10 times weaker binding affinity to SMYD1 compared to full-length HDGF.
- The C140 domain enhances DNA binding affinity and regulates sequence-specific binding of HDGF.

## Abstract

The protein-induced
fluorescence change technique was employed
to investigate the interactions between proteins and their DNA substrates
modified with the Cy3 fluorophore. It has been reported that the human
hepatoma-derived growth factor (HDGF), containing the chromatin-associated
N-terminal proline–tryptophan–tryptophan–proline
(PWWP) domain (the N-terminal 100 amino acids of HDGF) capable of
binding the SMYD1 promoter, participates in various
cellular processes and is involved in human cancer. This project investigated
the specific binding behavior of HDGF, the PWWP domain, and the C140
domain (the C-terminal 140 amino acids of HDGF) sequentially using
protein-induced fluorescence change. We found that the binding of
HDGF and its related proteins on Cy3-labeled 15 bp SMYD1 dsDNA will cause a significant decrease in the recorded Cy3 fluorophore
intensity, indicating the occurrence of protein-induced fluorescence
quenching. The dissociation equilibrium constant was determined by
fitting the bound fraction curve to a binding model. An approximate
10-time weaker SMYD1 binding affinity of the PWWP
domain was found in comparison to HDGF. Moreover, the PWWP domain
is required for DNA binding, and the C140 domain can enhance the DNA
binding affinity. Furthermore, we found that the C140 domain can regulate
the sequence-specific binding capability of HDGF on SMYD1.