Related Experiment Videos
Aberrant transcripts of the cyclin-dependent kinase-associated protein phosphatase in hepatocellular carcinoma
1Liver Research Unit, Chang Gung Memorial Hospital and Chang Gung University School of Medicine, Taipei, Taiwan. catyeh@ms14.hinet.net
Abstract:
The cyclin-dependent kinase (Cdk)-associated protein phosphatase (KAP) is a human dual specificity protein phosphatase that dephosphorylates Cdk2 on threonine 160 in a cyclin-dependent manner. To investigate whether mutations of this enzyme occur in hepatocellular carcinoma (HCC), KAP mRNA was analyzed by reverse transcription-PCR (RT-PCR), followed by cloning and sequencing. Eight of 14 biopsy tissues obtained from advanced HCC, 6 of 13 surgically removed HCC tissues, and 2 of the adjacent noncancerous tissues contained aberrant KAP transcripts. Using the yeast two-hybrid system, five of seven representative KAP mutants were shown to be defective in interacting with Cdk2. These data suggest a possible role of KAP mutations in multiple-step hepatocarcinogenesis.
Insights
Mutations in the cyclin-dependent kinase (Cdk)-associated protein phosphatase (KAP) gene were found in hepatocellular carcinoma (HCC) tissues. These KAP mutations may impair its interaction with Cdk2, suggesting a role in liver cancer development.
Area of Science:
- Biochemistry
- Molecular Biology
- Oncology
Background:
- The cyclin-dependent kinase (Cdk)-associated protein phosphatase (KAP) is a human enzyme crucial for regulating cell cycle progression.
- KAP dephosphorylates Cdk2 at threonine 160 in a cyclin-dependent manner, a key step in cell cycle control.
- Dysregulation of Cdk activity is implicated in various cancers, including hepatocellular carcinoma (HCC).
Purpose of the Study:
- To investigate the occurrence and functional significance of KAP gene mutations in hepatocellular carcinoma (HCC).
- To determine if identified KAP mutations affect its interaction with its substrate, Cdk2.
- To explore the potential role of KAP alterations in the multi-step process of hepatocarcinogenesis.
Main Methods:
- Analysis of KAP messenger RNA (mRNA) in HCC tissues using reverse transcription-polymerase chain reaction (RT-PCR).
- Cloning and sequencing of KAP transcripts to identify mutations.
- Functional assessment of KAP mutants using the yeast two-hybrid system to evaluate Cdk2 binding.
- Examination of KAP mRNA in both cancerous and adjacent noncancerous liver tissues.
Main Results:
- Aberrant KAP transcripts were detected in a significant proportion of HCC biopsy and surgically removed tissues (8/14 and 6/13, respectively).
- Abnormal KAP transcripts were also found in 2 of 13 adjacent noncancerous tissues.
- Five out of seven tested KAP mutants exhibited defective binding to Cdk2, indicating compromised protein-protein interaction.
- The identified mutations suggest a potential disruption of KAP's phosphatase activity or regulatory interactions.
Conclusions:
- Mutations in the KAP gene are present in hepatocellular carcinoma.
- These KAP mutations can impair the enzyme's ability to interact with Cdk2.
- Altered KAP function due to mutations may contribute to the development and progression of liver cancer.