KIAA0101 Human

What is KIAA0101 and what are its alternative nomenclatures?

KIAA0101 is a 111-amino acid human protein that functions primarily as a PCNA-binding factor involved in DNA replication and repair mechanisms. Researchers should be aware of its multiple alternative names in literature and databases, including PCNA-associated factor (PCLAF), PAF, PAF15, p15PAF, NS5ATP9 (Hepatitis C virus NS5A-transactivated protein 9), L5, OEATC-1 (Overexpressed in anaplastic thyroid carcinoma 1), and PCNA-clamp-associated factor . When conducting literature searches and database queries, researchers should incorporate these alternative designations to ensure comprehensive coverage of existing research.

What is the primary molecular function of KIAA0101 in normal cellular processes?

KIAA0101 functions as a critical regulator of DNA repair during DNA replication through its interaction with PCNA (Proliferating Cell Nuclear Antigen). During normal cellular function, KIAA0101 undergoes monoubiquitination at Lys-15 and Lys-24 during S phase, which promotes its association with PCNA . Following DNA damage, this interaction is disrupted, facilitating the association between monoubiquitinated PCNA and translesion DNA synthesis polymerase eta (POLH) at stalled replisomes. This process enables bypass of replication-fork-blocking lesions, maintaining genomic integrity . Additionally, KIAA0101 acts as a regulator of centrosome number, suggesting a role in ensuring proper chromosomal segregation during mitosis .

What experimental approaches are most effective for detecting KIAA0101 expression?

For optimal detection of KIAA0101 expression in experimental and clinical samples, researchers should employ multiple complementary methodologies:

• RNA-based detection: RT-qPCR and RNA-sequencing provide quantitative assessment of KIAA0101 transcription. RNA-seq additionally allows investigation of alternative splicing events, with evidence suggesting differential expression patterns between variant 1 (E001-E014) in cancer versus processed noncoding transcripts (E016) in normal tissues .

• Protein-based detection: Western blotting using recombinant KIAA0101 as positive control can reliably detect protein expression. The commercially available recombinant human KIAA0101 protein (such as ab171707) expressed in E. coli with >90% purity is suitable for such applications .

• Tissue localization: Immunohistochemistry with validated antibodies allows visualization of KIAA0101 distribution within tissue architectures. In normal adrenal cortex, for example, KIAA0101 shows sparse protein expression confined to adrenocortical progenitor cells, whereas expression is significantly elevated and widespread in adrenocortical carcinoma .

How is KIAA0101 expression typically dysregulated in cancer?

KIAA0101 shows significant expression dysregulation across multiple cancer types. Meta-analysis of four unique analyses in hepatocellular carcinoma (HCC) demonstrated KIAA0101 overexpression with a median rank of 31.5 (p=3.11E-22) . Individual studies report substantial fold increases in KIAA0101 transcripts in HCC compared to normal tissues:

• 9.085-fold elevation (p=1.37E-13) in one dataset (n=43)

• 6.943-fold increase (p=4.96E-92) in a larger cohort (n=445)

• 3.294-fold elevation (p=6.22E-22) in another dataset (n=197)

Similarly, in adrenocortical carcinoma, KIAA0101 mRNA and protein expression were 9.7-fold higher than in normal adrenal cortex (p<0.0001) .

The mechanisms of this overexpression appear multifactorial, as copy number variation (CNV) shows only weak positive correlation with gene expression, suggesting additional regulatory mechanisms beyond genomic amplification .

What gene networks and biological processes are associated with KIAA0101 in cancer?

WGCNA analysis has identified 31 genes significantly coexpressed with KIAA0101, with 12 upregulated and 9 downregulated along with KIAA0101 . Protein-protein interaction network analysis via STRING database revealed 9 key interaction partners that are also upregulated in HCC: STMN1, PTTG1, CCNB1, RACGAP1, KIF18A, TTK, ECT2, PARPBP, and PBK .

Gene Ontology analysis of KIAA0101-coexpressed genes revealed enrichment in critical cellular processes:

• Cellular Components: Centralspindlin complex and spindle (mitosis-associated structures)

• Molecular Functions: Coenzyme binding

• Biological Processes:

  • Nuclear chromosome segregation

  • Regulation of chromosome segregation

  • Mitotic spindle organization

  • Microtubule cytoskeleton organization during mitosis

  • Mitotic sister chromatid segregation

  • Regulation of spindle microtubule attachment to kinetochores

  • Actomyosin contractile ring assembly/organization

Of these processes, "regulation of attachment of spindle microtubules to kinetochores" showed the highest statistical significance in enrichment analysis . This comprehensive network analysis suggests KIAA0101 functions within a coordinated gene expression program governing mitotic processes and chromosomal stability.

How does KIAA0101 knockdown affect cancer cell phenotypes in experimental models?

Functional studies using siRNA-mediated knockdown of KIAA0101 in the NCI-H295R adrenocortical carcinoma cell line have revealed significant effects on cancer cell behavior :

• Anchorage-independent growth: KIAA0101 knockdown significantly decreased soft agar colony formation by 80% (p=0.001), indicating reduced tumorigenic potential

• Invasion capacity: KIAA0101 silencing reduced invasive capacity by 60% (p=0.006), suggesting a critical role in cancer cell invasion and potential metastasis

These experimental findings provide mechanistic evidence for KIAA0101's functional role in promoting aggressive cancer phenotypes and suggest that targeted inhibition of KIAA0101 might have therapeutic potential in KIAA0101-overexpressing cancers.

What is the prognostic significance of KIAA0101 in different cancer types and patient subgroups?

KIAA0101 expression has significant prognostic value across multiple cancer types, with detailed subgroup analyses revealing important demographic and clinical factors that influence its predictive power:

• Gender differences:

  • Male HCC patients: HR=2.6, p=0.00021

  • Female HCC patients: HR=1.87, p=0.03

• Disease stage impact:

  • Early-stage HCC: HR=2.34, p=0.00074

  • Advanced-stage HCC: HR=1.93, p=0.031

• Ethnic variations:

  • Asian patients: HR=4.68, p=0.00004

  • Caucasian patients: HR=1.74, p=0.018

These subgroup analyses reveal that KIAA0101's prognostic power is stronger in males than females, more pronounced in early-stage than advanced disease, and substantially greater in Asian than Caucasian populations . These findings have important implications for the clinical application of KIAA0101 as a biomarker, suggesting that patient demographics and disease characteristics should be considered when interpreting KIAA0101 expression data.

How does post-translational modification regulate KIAA0101 function during DNA damage response?

KIAA0101 undergoes complex post-translational modifications that dynamically regulate its function in DNA damage response pathways:

• Normal S phase: KIAA0101 is monoubiquitinated at Lys-15 and Lys-24, which promotes its association with PCNA during normal DNA replication

• DNA damage response: Following DNA damage, the monoubiquitin chains at Lys-15 and Lys-24 are extended to polyubiquitin chains, which disrupts the interaction with PCNA

• Functional consequence: This disruption enables monoubiquitinated PCNA to interact with translesion DNA synthesis polymerase eta (POLH) at stalled replisomes, facilitating bypass of replication-fork-blocking lesions

• Cell cycle regulation: KIAA0101 is polyubiquitinated by the APC/C complex at mitotic exit, leading to its degradation and ensuring proper regulation through the cell cycle

These precisely controlled modifications highlight KIAA0101's role as a molecular switch in the DNA damage response pathway, with ubiquitination status determining its functional interactions and cellular effects.

How can KIAA0101 expression be used to distinguish between benign and malignant neoplasms?

KIAA0101 expression demonstrates significant potential as a diagnostic biomarker for distinguishing between benign and malignant neoplasms, particularly in adrenocortical tumors:

In a study of 112 adrenocortical tissue samples (21 normal adrenal cortex, 80 benign adrenocortical tumors, and 11 adrenocortical carcinomas), KIAA0101 expression levels achieved 84% accuracy in differentiating adrenocortical carcinoma from normal and benign adrenocortical tumors . This diagnostic performance makes KIAA0101 a valuable tool in the often challenging clinical distinction between benign and malignant adrenocortical neoplasms.

Immunohistochemical analysis revealed an important pattern: in normal adrenal cortex, KIAA0101 protein expression was sparse and confined specifically to adrenocortical progenitor cells, whereas expression was significantly higher and more diffuse in adrenocortical carcinoma . This differential expression pattern provides both diagnostic utility and biological insights into KIAA0101's potential role in progenitor cell function.

What is the relationship between viral infection and KIAA0101 expression?

Evidence suggests a significant relationship between viral infection and KIAA0101 expression, particularly in the context of hepatitis viruses and HCC:

One of KIAA0101's alternative names, NS5ATP9 (Hepatitis C virus NS5A-transactivated protein 9), directly indicates its relationship with the HCV NS5A protein . In HCC studies, KIAA0101 expression levels and their prognostic implications appear particularly pronounced in Asian populations, where HBV infection is a predominant etiological factor in HCC development .

In a study involving eight pairs of HCC specimens and adjacent tissues, all eight patients were HBV-positive Chinese males, and KIAA0101 was identified among significantly upregulated genes in the HCC samples (adjusted p=0.00497) . These findings suggest potential mechanistic links between hepatitis virus infection and KIAA0101 dysregulation in hepatocarcinogenesis.

The association between viral infection and KIAA0101 expression may provide insights into virus-mediated oncogenesis pathways and could explain some of the variations in KIAA0101's prognostic significance observed across different patient populations .

What methodological considerations are important when designing experiments to study KIAA0101?

When designing experiments to investigate KIAA0101, researchers should consider several methodological factors to ensure robust and reproducible results:

• Expression analysis approaches:

  • Employ multiple detection methods (RT-qPCR, Western blot, immunohistochemistry) for comprehensive characterization

  • For recombinant protein work, consider commercially available human KIAA0101 protein expressed in E. coli with >90% purity, suitable for applications including SDS-PAGE and mass spectrometry

• Functional studies:

  • Design siRNA knockdown experiments targeting KIAA0101 to assess effects on cell proliferation, anchorage-independent growth, and invasion capacity

  • Consider multiple cell lines representing different cancer types where KIAA0101 is overexpressed

  • Include appropriate controls and validate knockdown efficiency at both mRNA and protein levels

• Clinical sample considerations:

  • Stratify analyses by critical demographic and clinical factors (gender, ethnicity, disease stage) that influence KIAA0101's expression patterns and prognostic significance

  • Ensure proper matching of tumor and adjacent normal tissues from the same patients when possible

  • Consider the potential influence of viral infection status (particularly HBV/HCV) on KIAA0101 expression

• Coexpression analysis:

  • Implement weighted gene co-expression network analysis (WGCNA) to identify genes functionally related to KIAA0101

  • Validate key interactions through protein-protein interaction studies

  • Perform pathway enrichment analysis to contextualize KIAA0101's role in broader cellular processes

• Data interpretation:

  • Account for alternative splicing patterns, particularly differences between variant 1 (E001-E014) and processed noncoding transcripts (E016)

  • Consider potential confounding factors such as copy number variation when interpreting expression data

Adherence to these methodological considerations will enhance the rigor and reproducibility of KIAA0101 research and facilitate more meaningful comparisons across studies.

What are the current limitations in our understanding of KIAA0101 in cancer biology?

Despite significant advances in KIAA0101 research, several important knowledge gaps remain:

• The complete spectrum of molecular mechanisms by which KIAA0101 promotes cancer progression beyond its interaction with PCNA requires further elucidation. While its role in DNA repair is established, its contributions to other cancer hallmarks need deeper investigation .

• The specific transcriptional and post-transcriptional regulatory mechanisms controlling KIAA0101 expression in cancer remain incompletely characterized. The weak correlation between copy number variation and expression suggests additional regulatory layers that need to be identified .

• The therapeutic potential of targeting KIAA0101 has not been extensively explored despite promising functional study results showing that knockdown reduces tumorigenic and invasive properties .

• The interplay between KIAA0101 and the tumor microenvironment, including potential roles in modulating immune responses, represents an underexplored area.

• The intriguing association between viral infection (particularly hepatitis viruses) and KIAA0101 expression warrants deeper mechanistic investigation to understand how viral factors might regulate this protein .

Addressing these knowledge gaps could lead to improved diagnostic approaches and potential therapeutic strategies targeting KIAA0101 in various cancer types where it is overexpressed and associated with poor prognosis.

What future research directions might advance our understanding of KIAA0101 function?

Several promising research directions could significantly advance our understanding of KIAA0101's role in normal biology and disease:

• Structural biology approaches to characterize the molecular details of KIAA0101 interactions with PCNA and other binding partners, potentially informing rational drug design efforts.

• Single-cell analyses to investigate cell-type specific expression patterns of KIAA0101, particularly in cancer with heterogeneous cell populations.

• Liquid biopsy studies to evaluate KIAA0101 as a circulating biomarker for early cancer detection and treatment response monitoring.

• CRISPR-based functional genomics to systematically identify synthetic lethal interactions with KIAA0101 overexpression, potentially revealing new therapeutic vulnerabilities.

• Development of small molecule inhibitors targeting the KIAA0101-PCNA interaction based on the established role of this interaction in cancer cell survival and proliferation.

• Integration with immune profiling to understand potential relationships between KIAA0101 expression and tumor immune microenvironment characteristics.

• Expanded analysis of KIAA0101 expression across diverse cancer types and patient populations to further refine its utility as a prognostic and predictive biomarker.