It explaines DNA repair mechanisms with perfect GIF Videos DNA Damage and DNA repair mechanism in Space DNA repair systems in Both prokaryotes and eukaryotes

1. DNA Damage and
Responses in
Space
Presented by
Basavalingayya
PGS18AGR7801

2. Contents
 Introduction
 Overview of DNA damage and responses (DDRs)
 DNA repair mechanisms
 Spaceflight environment
 DNA damage and responses in space
 Microgravity and its effects on DDRs
 Space radiation and its effects on DDRs
 Approaches to reduce DNA damage effects
 Importance of DNA repair mechanisms
 Conclusion

3. Introduction
 DNA damage is a common routine in a cell life cycle and it is
corrected by different repair pathways.
 In space environment the Intensity of DNA damage is very high
in space as expected because of several factors.
 But when we see the DNA repair mechanisms in space, many
studies are reported that, “so for, there is no differential DNA
damage repair mechanisms has been discovered in space
condition compared to Earth.”

4. What is DNA
damage and
repair ?
DNA damage is an alteration in the chemical structure of DNA,
such as a break in a strand of DNA, a base missing from the
backbone of DNA, or a chemically changed base.
 DNA damage can occur naturally or via environmental factors.
DNA repair is a collection of processes by which a cell identifies
and corrects damage to the DNA molecules that encode its
genome.
Oliver et al., 2004

5. Efficient DNA replication
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(how the DNA damage occur and how it will be corrected by the cell, all we’ll see in later slides))

6. Overview of DNA damage and responses (DDRs)
Siu-Hong et al., 2010

7. Types of DNA damage

8. Department of Biotechnology 8Solali et al., 2010

9. DNA damage check points
9
 The global response to damage is an act directed toward the
cells own preservation and triggers multiple pathways of
macromolecular repair, lesion bypass, tolerance, or apoptosis.
 The common features of global response are induction of
multiple genes, cell cycle arrest, and inhibition of cell division).
 After DNA damage, cell cycle checkpoints are activated
checkpoint activation pauses the cell cycle and gives the cell
time to repair the damage before continuing to divide.
 DNA damage checkpoints occur at the G1/S and G2/M
boundaries.
 Checkpoint activation is controlled by two master kinases, ATM
and ATR.
Department of Biotechnology

10. Cont…
10
 ATM responds to DNA double-strand breaks and disruptions in
chromatin structure, whereas ATR primarily responds to stalled
replication forks.
 These kinases phosphorylate downstream targets in a signal
transduction cascade, eventually leading to cell cycle arrest.
Department of Biotechnology
Kaufmann et al., 1996

11. DNA Repair Mechanisms
 Direct reversal
Photo-reactivation
Methyltransferase
 Excision repair
Base Excision Repair (BER)
Nucleotide Excision Repair (NER)
 Mismatch repair (MMR)
 Recombinational repair
Homologous recombination (HR)
Non-homologous end joining (NHEJ)
 The error-prone (SOS) repair system
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12. Photo-reactivation
Olaf et al., 2002
Mammals seem to possess all of the repair mechanisms found
in E. coli except photo-reactivation, as most mammalian cells
do not have access to light.

13. Methyltransferase
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Methylation of DNA by
alkylating agents
Direct Repair: Reversal of O6 methyl G
to G by methyltransferase
Lisa et al., 2013

14. Base Excision Repair (BER)
Oliver et al., 2004

15. Nucleotide Excision Repair (NER)
Used by the cell for bulky DNA damage – First identified in 1964 in E.coli.
– Chemical adducts
– UV photoproducts (thymine-thymine dimers)
Oliver et al., 2004

16. Nucleotide Excision Repair in Eukaryotes
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Two major pathways
 Global genome repair
 Transcription coupled repair

17. 17Olaf et al., 2002

18. Mismatch repair (MMR)
18Oliver et al., 2004

19. Nicholas et al., 2017

20. The error-prone (SOS) repair system
Janion et al., 2008

21. Effects of DNA damage
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DNA damage, if not repaired, may affect replication and
transcription, leading to mutation or cell death
Mutation
researchgate.net

22. Department of Biotechnology 22
leads to mutation
MUTATION
(a permanent change
can not be repaired)
Unrepaired
jonlieffmd.com

23. What is Spaceflight..??
Spaceflight is ballistic flight into or through outer space.
Spaceflight can occur with spacecraft with or without humans
onboard.
International Space Station (ISS) is a space station, or a
habitable artificial satellite, in low Earth orbit.
Orbit height: 408 km Length: 72.8 m Width: 108.5 m
Frederick et al., 2012

24. Does ISS has the
Gravity??
24Department of Biotechnology
In ISS their is no force to attract
therefore water flies in ISS and
never fall down as on earth. The
surface tension of water molecules
binds water in a shape of ball and
prevents water to flow as we
generally see on earth.
The ISS has the system of acceleration
environment on the station ranges from
transient episodes of 0.01 g to below
one millionth of 1 g.
NASA Knows! (Grades 5-8), 2016

25. DNA damage in space
Space is actually a pretty hazardous place, and radiation is one of
the biggest concerns. On an average the astronauts are
subjected to around 30 times the radiation a human receives in a
year on Earth.
 Intensity of DNA damage is very high in space as expected
because of following reasons.
Spaceflight (the ISS and beyond) Earth (Normal level for
living organisms)
 Temperature extremes (100 to –100oC)
 Acoustic noise (noise on the ISS is 60 dB)
 Space debris (>12000 debris objects larger
than 10 cm)
 Ionizing radiation (425 μSv/day or 0.3 Sv/year)
 Microgravity < 1 μg (0.01 g to quasi-steady
levels below one millionth of 1 g)
 5 to 45oC (Normal
temp. condition)
 34 decibel
 ---
 0.01 Sv/year
 1 g
Robert et al., 2009

26. The space radiation sources are
 Galactic cosmic rays (GCR) : Consist of approximately 87%
hydrogen ions (protons) and 12% helium ions.
 Protons released from large solar particle events (SPEs)
Effects on DDR :
 Space radiation can cause damage to DNA directly, through
the interaction of charged particles with the DNA molecules
themselves.
Space radiation and
effects
Moreno-Villanueva et al., 2017

27. Microgravity and
effects
Microgravity is when things seem to be weightless. "Micro-"
means "very small." Microgravity is when the pull of gravity is not
very strong (equivalent to millionth of 1 g).
Effects on DDR
 Impact on DNA repair resulting in accumulation of severe DNA
lesions. Ultimately these lesions, namely double strand breaks,
chromosome aberrations.
Moreno-Villanueva et al., 2017

28. DNA damage responses in space
Most of the studies shown that, so for, there is no differential DNA
damage repair mechanisms has been discovered in space
condition compared to Earth.
The effects of microgravity on ligase activity in the repair of
DNA double-strand breaks (Takahashi et al., 2009).
 The DNA repair activity of T4 DNA ligase was measured in vitro
for a DNA substrate damaged by restriction enzyme (Sma1)
digestion during a US Space Shuttle mission.
 After the flight, the ligated DNA molecules was confirmed using
an electrophoresis method.

29. System used to carry out enzymatic reactions

30. 30Department of Biotechnology
T4 DNA ligase activity at 4 or 22.50
C on the ground

31. Almost no difference between the T4 DNA ligase activity in space and ground
control.
Rejoining of DNA dsb.
(A) Typical pattern after gel electrophoresis. Lane U, untreated pRC; lane L, pRC
digested by Sma I; lane M, molecular markers. Lanes 0, 0.1, 0.3, 1 and 3,
concentration of T4 DNA ligase (U/µg).
(B) (B) Measurement of the density of DNA bands produced by ligation at room
temperature (21.6–22.1ºC) for 10 h. Closed symbols, on earth; open symbols,
in space. Circles, ligated product (ccDNA, ocDNA and multimeric ligated
products); triangles, ccDNA.

32. Other spaceflight studies for DDRs
 Up- and down-regulation of some genes related to DNA repair
mechanism.
 Expression of some new genes related to DNA repair
mechanism.
Effects of microgravity on DNA damage response in C.
elegans during Shenzhou-8 spaceflight (Ying et al., 2015).

33. Analysis of global gene expression profile under different
spaceflight conditions.
(A) A Venn diagram illustrating number of total transcripts,
differentially expressed transcripts under SF environment and
SR environment, and overlap among these data.
(B) Ratio of differentially expressed transcripts under spaceflight
conditions.

35. Microarray data validation by qRT-PCR
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36. Discussion
36
In this study, gene expression profile and miRNA expression
profile in larvae of C. elegans during Shenzhou-8 spaceflight
mission were analyzed. Results indicate that during the short-
duration spaceflight, microgravity probably enhanced the
biological response on transcription and post-transcriptional
regulation, in particular on DDR process, and these findings
suggest how safe or hazardous the radiation combined with
microgravity exposure is for the astronauts, which may be helpful
for space risk assessment.
Department of Biotechnology

37.  The spaceflight environment has also shown the significant
increase in telomere length and chromosome aberrations.
The NASA Twins Study: A multidimensional analysis of a
year-long human spaceflight (Bakelman et al., 2019).
To understand the health impact of long-duration spaceflight, one
identical twin astronaut was monitored before, during, and after a
1-year mission onboard the ISS, his twin served as a genetically
matched ground control
Telomere length and DNA damage responses

38.  Here, average telomere length was evaluated pre-, in-, and
post-flight (DNA; peripheral blood mononuclear cells) using
quantitative real-time polymerase chain reaction.
 The chromosome aberrations were analyzed by detecting
interchromosomal translocations and intrachromosomal
inversions.
Scott KellyMark Kelly

39. Telomere length dynamics and DNA damage responses.
(A) Relative average telomere length in PBMCs (DNA) pre-, in-,
and postflight assessed by qRT-PCR for HR (green) and TW
(blue).
(B) Relative average telomere length for TW in sorted PBMC
surpopulations, CD19 B cells, CD4 and CD8 T cells, pre-, in-,
and postflight.

40. Results (Telomere length dynamics)
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Fig. 2. Telomere length dynamics and DNA damage responses.
(C and D) Telo-FISH–generated histograms of individual telomere length
distributions [shorter to longer, lower to higher relative fluorescent intensity
(RFI)] for HR (C) and TW (D) preflight (blue), inflight (red), and postflight
(green).

41. (E) Analysis of DNA damage utilizing dGH (Directional
genomic hybridization) paints (pink) for chromosomes 1, 2, and
3 facilitated simultaneous detection of translocations and
inversions. Representative image of dGH on a metaphase
chromosome spread illustrating an intrachromosomal inversion
(yellow arrow) and an interchromosomal translocation (white
arrows).
(F) Quantification of translocation (striped bars) and inversion
(solid bars) frequencies for HR and TW pre-, in-, and postflight.

42. At present the astronauts were studying how DNA repair
mechanisms work in space, so they snipped through strands of
the fungus's genetic code in a number of places to mimic
radiation damage.
"The damage actually happens on the space station and the
analysis also happens in space," that they have designed the
DNA lab aboard the ISS. “To understand if DNA repair methods
are different in space than on Earth."
The results
are yet to
be publish

43. Rotating Wall Vessel (RWV) Aiming to construct a machine that
allows the simulation of weightlessness (microgravity), the
RWV was developed.
Simulated
microgravity and
effects

44. Department of Biotechnology 44Moreno-Villanueva et al., 2017

45. Department of Biotechnology 45

46. Approaches to reduce DNA damage and its effects
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 Chemosanitization by targeting DNA damage check points.
 Targeting DNA Repair in Cancer: Beyond PARP Inhibitors.
 Targeting DNA repair pathways: A novel approach to reduce cancer
therapeutic resistance.
Jessica et al., 2017

47. CONCLUSION

49. Questions
1. What is DNA damage?
2. What is spaceflight?
3. What are the sources for DNA damage both on Earth and space?
4. What are the DNA repair mechanisms?
5. What are the effects of DNA damage?
6. What is microgravity and how it affects DNA repair mechanisms?
7. What is space radiation and how it affects DNA repair mechanisms?
8. What are Pros and Cons of DNA repair mechanisms?
9. What are the approaches to reduce DNA damage and its effects?