DNA Damage Caused byUltraviolet RadiationBy: Nicolle A. Rosa MercadoBy: Nicolle A. Rosa MercadoBy: Nicolle A. Rosa Mercado
Introduction-DNA:-Most important molecule for everyliving organism-Contains the instructions necessaryfor every living organism to function-Alterations in it may lead to geneticdisorders and cancer-Ultraviolet (UV) radiation:-Uncontrollable environmental factorthat alters DNA sequences-Its damage may cause cells to restrainRNA synthesis (Moné MJ et. al 2001)Fig. 1: This image is an exampleof a possible alteration in a DNAsequence.earthobservatory.nasa.gov
UV Radiation-Type of electromagnetic radiation that has ashorter wavelength than that of the visible light.-Three types of UV radiation:- UV-A (400nm-315nm): found in black lights- UV-B (315nm-280nm): most dangerous type- UV-C (280nm-200nm): germicidalFig. 2: This image is anexplanation of the lightspectrumflightspectrumllc.com
How UV radiation may be beneficial-May create resistance to certainpathogens in plants-Used as a treatment for people withvitiligo for humans-Used to purify drinking water due to itsgermicidal properties-Helpful in studies that involvespectophotometry and molecular genetics.Fig. 3: This image shows the handsof a vitiligo patient. UV-B light isused to restore the pigmentationof their skin.Fig. 4: This image shows the machineryused to purify drinking waterwith UV radiation
Cyclobutane pyrimidine dimers (CPDs)and 6-4 photoproducts(6-4 PPs)-Lesions in the DNA sequence caused by UVexposure (De Lima-Bessa KM et. al. 2007)-May be responsible for the formation of clusters thatmight lead to skin carcinomas-Promote apoptosis provoked by UV exposure incells that lack NER-Can obstruct DNA transcription and replication-Fixed through DNA repair mechanisms
DNA Repair Mechanisms-Cannot always detect the mutations due to defects in therepair mechanisms themselves-Important for maintaining the DNA sequence stable.-A type of DNA repair mechanism is nucleotide excisionrepair (NER), which corrects different types of damagesincluding thymine dimers provoked by UV radiation.(http://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344)
NER Flow ChartFig. 5: This image shows how NER works. It consists of four proteins UvrA, UvrB,UvrC, and UvrD. UvrA and UvrB search for mutations in the sequence, UvrC makescuts in the region of mutations so UvrD can remove them from the sequence. DNApolymerase and DNA ligase then restore the sequence to the way it was before themutation occurred.http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation33.html
UV radiation and cancer-Three types of cancer caused by UV radiation:-Basal Cell Carcinoma: innermost part of theepidermis; not a big threat-Squamous Cell Carcinoma: upper part of theepidermis; not a big threat-Melanoma: most dangerous type of skin cancer;develops in skin cells known as the melanocytes
UV radiation and cancerFig.6: This image shows howsquamous cell carcinomas andbasal cell carcinomas look on theouter part of the epidermis.Fig. 7: This image demonstrateshow melanoma affects theinner and outer epidermis andthe dermis.
-It is very important to understand this topic due to the fact thatUV radiation is an uncontrollable factor that can affect our healthin a great way.-Understanding how UV radiation relates to DNA repairmechanisms might help with the discovery of new techniques tomaintain stability in DNA sequences.Importance of this study
Conclusion-DNA is the most important molecule in every organism and it is highlysusceptible to UV radiation.-Although DNA has highly specific repair mechanisms, some mutationscaused by UV can be ignored due to a defect in the repair mechanism.-Ultra-violet radiation causes DNA damage such as CPDs and 6-4 PPs thatmay lead to cancer.-Melanoma is the most dangerous type of skin cancer.-UV radiation presents a mayor threat to our health because of its abilityto damage DNA sequences.
References-Bernard A. Kunz, Paige K. Dando, Desma M. Grice, Peter G. Mohr, Peer M. Schenk, and David M. Cahill,(October 2008), UV-Induced DNA Damage Promotes Resistance to the Biotrophic PathogenHyaloperonospora parasitica in Arabidopsis, Rockville, United States, American Society of PlantBiologists,148:1021-1031-de Lima-Bessa KM, Armelini MG, Chigancas V, Jacysin JF, Amarante-Mendes GP, Sarasin A, Menck CFM,(December 2007), CPDs and 6-4PPs play different roles in UV-induced cell death in normal and NER-deficient human cells, Brazil, DNA Repair, 7:303-312-Hidawi. June 2010. India. September 2010. Available at:http://www.hindawi.com/journals/jna/2010/592980/-Moné MJ, Volker M, Nikaido O, Mullenders LHF, van Zeeland AA, Vershure PJ, Manders EMM, van DrielR, (September 2001), Local UV-induced DNA damage in cell nuclei results in local transcription inhibition,Amsterdam, EMBO Reports, 21:1013-1017-Nijhofa JGW, Muldera, Aat M, Speksnijderb, Ewoud N, Hoogervorstb, Esther M, Mullendersc, Leon HF,De Gruijl, Frank R, (July 2007), Growth stimulation of UV-induced DNA damage retaining epidermal basalcells gives rise to clusters of p53 overexpressing cells, The Netherlands, DNA Repair 6:1642-1650-Oh K, Bustin M, Mazur S, Appellac E, Kraemer K, (September 2010), UV-induced histone H2AXphosphorylation and DNA damage related proteins accumulate and persist in nucleotide excision repair-deficient XP-B cells, United States, DNA Repair, 10:5-15.-Scitable. 2008. Nature Education. 2008. Available at: http://www.nature.com/scitable/topicpage/dna-damage-repair-mechanisms-for-maintaining-dna-344