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Cervical squamous intraepithelial lesion (SIL), previously called cervical intraepithelial neoplasia (CIN), is a form of dysplasia that can progress to cervical cancer. The term carcinoma in situ may be used interchangeably with high-grade SIL. [8] Ductal carcinoma in situ of the breast is the most common precancer in women.
The cause of CIN is chronic infection of the cervix with HPV, especially infection with high-risk HPV types 16 or 18. It is thought that the high-risk HPV infections have the ability to inactivate tumor suppressor genes such as the p53 gene and the RB gene, thus allowing the infected cells to grow unchecked and accumulate successive mutations, eventually leading to cancer.
The Papanicolaou test (abbreviated as Pap test, also known as Pap smear (AE), [1] cervical smear (BE), cervical screening (BE), [2] or smear test (BE)) is a method of cervical screening used to detect potentially precancerous and cancerous processes in the cervix (opening of the uterus or womb) or, more rarely, anus (in both men and women). [3]
The Pap test can be used as a screening test but produces a false negative in up to 50% of cases of cervical cancer. [58] [59] Another concern is the cost of doing Pap tests, which makes them unaffordable in many areas of the world. [60] Confirmation of the diagnosis of cervical cancer or precancer requires a biopsy of the cervix.
Numerical CIN is a high rate of either gain or loss of whole chromosomes; causing aneuploidy.Normal cells make errors in chromosome segregation in 1% of cell divisions, whereas cells with CIN make these errors approximately 20% of cell divisions.
Furthermore, 1/3 of CpG sites in mitochondrial DNA were associated with increased methylation in CIN3+. [108] Thus, a correlation exists between CIN3+ and increased methylation of CpG sites in the HPV16 L1 open reading frame. [108] This could be a potential biomarker for future screens of cancerous and precancerous cervical disease. [108]
Transcription preinitiation complex, represented by the central cluster of proteins, causes RNA polymerase to bind to target DNA site. The PIC is able to bind both the promoter sequence near the gene to be transcribed and an enhancer sequence in a different part of the genome, allowing enhancer sequences to regulate a gene distant from it.
Nucleosomes are portions of double-stranded DNA (dsDNA) that are wrapped around protein complexes called histone cores. These histone cores are composed of 8 subunits, two each of H2A, H2B, H3 and H4 histones. This protein complex forms a cylindrical shape that dsDNA wraps around with approximately 147 base pairs.