Cloning and expression of a new HOXC6 transcript encoding a repressing protein

Area of Science:

• Molecular Biology
• Cancer Research
• Genetics

Background:

• Homeodomain-containing proteins (HOX) are crucial transcription factors regulating development and cell differentiation.
• Aberrant HOX gene expression is implicated in various cancers, including breast cancer.
• Understanding HOX gene expression in breast cancer is vital for comprehending malignant transformation.

Purpose of the Study:

• To characterize expressed homeobox (HOX) genes in breast cancer cells.
• To identify and analyze novel HOXC6 transcripts and their encoded proteins.
• To investigate the functional role of HOXC6 in breast cancer cells.

Main Methods:

• Cloning of HOXC6 transcripts from MCF7 breast cancer cell line cDNA library.
• Quantitative analysis of HOXC6 transcript abundance in cancer versus non-tumorigenic cell lines.
• Detection of HOXC6 expression in breast tumor tissues.
• Transient co-transfection experiments to assess transcriptional repression and co-operation with other HOX proteins.

Main Results:

• Two distinct HOXC6 transcripts were cloned, one encoding a novel homeodomain-containing protein with a unique N-terminal sequence.
• The novel HOXC6 transcript was found to be less abundant in human breast cancer cells compared to non-tumorigenic cell lines.
• HOXC6 transcripts were detected in breast carcinomas, adjacent tissues, and various other human tumors.
• Both HOXC6 transcripts repressed transcription from a HOX binding sequence and co-operated with other HOX proteins (e.g., HOXB7).

Conclusions:

• HOXC6 proteins, including the novel variant, may influence breast cell phenotype.
• These proteins likely exert their function through co-operative interactions with other HOX proteins.
• Repression of target genes by HOXC6 proteins is a key aspect of their function in breast cells.