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Identification of multiple repeat sequences and transcription-related elements within introns 4, 8 and 9 of human
1Department of Radiation Medicine, Lombardi Cancer Center, Georgetown University, Washington, D.C. 20007.
Abstract:
Oncogenic activation of the human c-raf-1 protein (Raf-1) occurs by truncation of its aminoterminus (regulatory domain) and retention of the carboxyterminus (kinase domain). To gain insight into the structure of human raf-1 genomic DNA corresponding to the regulatory domain of Raf-1, we analyzed the nucleotide sequences of introns 4, 8, and 9. Very high frequencies of the direct and indirect repeats, and A/T nucleotides were observed within introns 4, 8, and 9; and the DNA sequences, 5'-TTAGTCA-3' and 5'-TGATTCA-3', like the DNA recognition site of transcription factor AP-1, were identified within intron 4 of raf-1 in human normal and tumor DNAs. In addition, several transcriptional elements (CAAT box, TATA sequences, eukaryotic transcription initiation sites, and cellular transcriptional elements) were found within introns 4, 8, and 9 of human raf-1. These data suggest: 1) the high frequency of intron-specific repeats is a possible recombinational mechanism for derivation of truncated oncogenic forms of Raf-1; and 2) the multiple transcriptional elements within introns 4, 8, and 9 may have important implications in the regulation of raf-1 transcription and, therefore, its role in cell growth and proliferation.
Insights
Genomic analysis of the human c-raf-1 gene reveals repeat sequences and transcriptional elements within introns 4, 8, and 9. These findings suggest mechanisms for oncogenic Raf-1 (Rapidly Accelerated Fibrosarcoma-1) formation and regulation.
Area of Science:
- Molecular Biology
- Genomics
- Cancer Research
Background:
- Oncogenic activation of human c-raf-1 (Raf-1) involves truncation of its regulatory domain.
- Understanding the genomic structure of Raf-1 is crucial for cancer research.
Purpose of the Study:
- To investigate the nucleotide sequences of introns 4, 8, and 9 of the human raf-1 gene.
- To identify potential regulatory elements and structural features within these introns.
Main Methods:
- Analysis of nucleotide sequences of introns 4, 8, and 9 in human raf-1.
- Identification of direct and indirect repeats, A/T-rich regions, and transcriptional elements.
Main Results:
- High frequencies of repeats and A/T nucleotides were found in introns 4, 8, and 9.
- AP-1 transcription factor recognition sites were identified in intron 4.
- Various transcriptional elements, including CAAT and TATA sequences, were present in introns 4, 8, and 9.
Conclusions:
- Intron-specific repeats may facilitate the generation of truncated, oncogenic Raf-1 forms.
- Transcriptional elements within these introns could play a role in regulating raf-1 gene expression and cell proliferation.