title: Class I and II Small Heat Shock Proteins Together with HSP101 Protect Protein Translation Factors during Heat Stress.
abstract: The ubiquitous small heat shock proteins (sHSPs) are well documented to act in vitro as molecular chaperones to prevent the irreversible aggregation of heat-sensitive proteins. However, the in vivo activities of sHSPs remain unclear. To investigate the two most abundant classes of plant cytosolic sHSPs (class I [CI] and class II [CII]), RNA interference (RNAi) and overexpression lines were created in Arabidopsis (Arabidopsis thaliana) and shown to have reduced and enhanced tolerance, respectively, to extreme heat stress. Affinity purification of CI and CII sHSPs from heat-stressed seedlings recovered eukaryotic translation elongation factor (eEF) 1B (α-, β-, and γ-subunits) and eukaryotic translation initiation factor 4A (three isoforms), although the association with CI sHSPs was stronger and additional proteins involved in translation were recovered with CI sHSPs. eEF1B subunits became partially insoluble during heat stress and, in the CI and CII RNAi lines, showed reduced recovery to the soluble cell fraction after heat stress, which was also dependent on HSP101. Furthermore, after heat stress, CI sHSPs showed increased retention in the insoluble fraction in the CII RNAi line and vice versa. Immunolocalization revealed that both CI and CII sHSPs were present in cytosolic foci, some of which colocalized with HSP101 and with eEF1Bγ and eEF1Bβ. Thus, CI and CII sHSPs have both unique and overlapping functions and act either directly or indirectly to protect specific translation factors in cytosolic stress granules.
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Fionn
authors.identifier: 0000-0002-2430-5074
authors.initials: F
authors.lastname: McLoughlin
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Eman
authors.initials: E
authors.lastname: Basha
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Mary E
authors.initials: ME
authors.lastname: Fowler
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Minsoo
authors.initials: M
authors.lastname: Kim
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Juliana
authors.initials: J
authors.lastname: Bordowitz
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.).
authors.forename: Surekha
authors.initials: S
authors.lastname: Katiyar-Agarwal
authors.affiliation: Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003 (F.M., M.E.F., M.K., E.V.);Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (E.B., M.K., J.B., S.K.-A.); andDepartment of Botany, Tanta University, Tanta 31527, Egypt (E.B.) vierling@biochem.umass.edu.
authors.forename: Elizabeth
authors.identifier: 0000-0002-0066-4881
authors.initials: E
authors.lastname: Vierling
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D039601:Eukaryotic Initiation Factor-4A / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D050888:Heat-Shock Proteins, Small / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D015151:Immunoblotting; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological; D053719:Tandem Mass Spectrometry; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C115569:HSP101 protein, plant; D050888:Heat-Shock Proteins, Small; D010445:Peptide Elongation Factors; D010940:Plant Proteins; D020033:Protein Isoforms; D021122:Protein Subunits; D014157:Transcription Factors; D039601:Eukaryotic Initiation Factor-4A