Abstract

Viralresistanceisessentialinallkingdomsoflife,althoughdiverseorganismshave evolvedequallydiversemechanismsforcombattinginfection.Inbacteriaandarchaea,the CRISPR(clusteredregularlyinterspacedshortpalindromicrepeats)adaptiveimmunesystem clearsinvadingDNAduringinfectionthroughasmall-RNAguidedinterferencemechanism. CRISPRimmunityproceedsthroughtwostages:adaptation,inwhichfragmentsofinvasive DNAfrombacteriophagesorplasmidsareinsertedasspacerswithintheCRISPRlocusofthe hostgenomeandsubsequentlyserveastemplatesfortheproductionofsmallguideCRISPR (cr)RNAs;?andinterference,duringwhichthecrRNAanditseffectorCRISPRassociated(Cas) proteinsbindcomplementarytargetregionsoftheinvadingDNA,leadingtoitsdestructionbya Casendonuclease.Ourgoalistodefinehowbacteriamaximizetheirimmunecapacitytogain anadvantageinthemoleculararmsraceagainsttheirinvaders.Ourfirstgoalistounderstand thesequence-dependenceofimmunesystemevasionthroughthedevelopmentofpoint mutationswithintheinvadingDNA.Ourpreviousstudieshaverevealedthatspacersequence greatlyinfluencestheeffectivenessofthese?escape?mutations,suggestingforthefirsttime thatsomespacersequencesprovidestrongerimmunitythanothers.Inaddition,wehave discoveredthatduringinitialinfection,bacteriauseatwo-tiereddefensivesystemtobroaden theiradaptationcapacity.Wewillevaluatetheimpactofthistacticonhostimmunityand elucidatethemolecularmechanismsunderlyingthisdefensestrategy.Finally,wewilldetermine thestructuralbasisforrapidadaptationtriggeredwhentheCRISPRmachinerysensesnon- canonicaltargetsequences.Ourstudieswillhavemajorimplicationsontheunderstandingof host-virusinteractionsandco-evolution,animportantdeterminantofthecompositional dynamicswithincomplexecologicalsystemsincludingthehumanmicrobiome.

Public Health Relevance

Bacterialcompositionwithinthehumanmicrobiomehasmajorimplicationsonseveralaspects ofhumanhealth,includingmetabolism,diseaseandimmunity.CRISPRadaptiveimmune systemsstronglyinfluenceinteractionsbetweenbacteriaandbacteriophageswithinthe microbiome,helpingtoshapebacterialcompositionwithinthesecommunities.Ourworkwill definehowbacteriamaximizetheirabilityadapttoanddefendagainstimmunesystemevasion byinvasiveelements,thecrucialeventsthatdrivepopulationdynamicswithinthemicrobiome.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM115874-01A1
Application #
9177303
Study Section
Prokaryotic Cell and Molecular Biology Study Section (PCMB)
Program Officer
Bender, Michael T
Project Start
2016-09-02
Project End
2021-08-31
Budget Start
2016-09-02
Budget End
2017-08-31
Support Year
1
Fiscal Year
2016
Total Cost
$303,866
Indirect Cost
$93,866

  Institution

Name
Iowa State University
Department
Biochemistry
Type
Schools of Arts and Sciences
DUNS #
005309844
City
Ames
State
IA
Country
United States
Zip Code
50011

  Publications

Lee, Hayun; Zhou, Yi; Taylor, David W et al. (2018) Cas4-Dependent Prespacer Processing Ensures High-Fidelity Programming of CRISPR Arrays. Mol Cell 70:48-59.e5
Murugan, Karthik; Babu, Kesavan; Sundaresan, Ramya et al. (2017) The Revolution Continues: Newly Discovered Systems Expand the CRISPR-Cas Toolkit. Mol Cell 68:15-25
Xue, Chaoyou; Zhu, Yicheng; Zhang, Xiangmei et al. (2017) Real-Time Observation of Target Search by the CRISPR Surveillance Complex Cascade. Cell Rep 21:3717-3727
Xue, Chaoyou; Whitis, Natalie R; Sashital, Dipali G (2016) Conformational Control of Cascade Interference and Priming Activities in CRISPR Immunity. Mol Cell 64:826-834