Study On The Modulation Of APOBEC3H On SVA Retrotransposition

SINE-VNTR-Alus(SVA)is a non-autonomous retrotransposon.With the help of LINE-1 ORF2 p,SVA RNA is inserted into the new genomic site through the trans-retrotransposition process.During human evolution,SVA is the youngest retrotransposons and still keeps the transposition activity.SVA affects the host through a variety of mechanisms,including insertional mutagenesis,exon rearrangement,alternative splicing,and differential methylation Furthermore SVA retrotransposites are involved in the occurrence of some diseasesMammalian cells have evolved a series of defense mechanisms to counter the adverse effects of retrotransposons in the genome.The cytosine deaminase APOBEC3 H family as a host-restricted factor has been shown to have the ability to inhibit multiple viruses and retrotransposition activity of LINE-1,but the modulation of APOBEC3 H on SVA retrotransposition is unclear.This study demonstrates that APOBEC3 H proteins play important roles in the regulation of SVA retrotransposition activity.Hererin we explore the possible functional domains of APOBEC3H_HapII which are responsible for HIV-1 restriction and confirm that the mechanisms of APOBEC3H_HapII on suppressing SVA retrotransposition are different from that of inhibiting HIV-1.In addition,we explore whether APOBEC3 H have the abililty of binding with SVA RNA.Sucrose density gradient centrifugation,immunofluorescence assay,Western blot and qPCR are used to explore the mechanisms in this study.We demonstrated that A3H_HapII have the ability of binding with SVA RNA.A3H_HapII promoted the formation of stress granules by up-regulating phosphorylation of eIF2?,which in turn blocked the transposition of SVA.Meanwhile,we illustrated that MG132 inhibits the degradation of A3 H unstable haploytpes,including A3H_HapI,HapIII,HapIV and HapVI.It indicates that A3 H unstable haplotypes are degraded through ubiquitination proteasome pathway.A3 H unstable haplotypes have the similar inhibitory effects on SVA retrotransposition as A3 H unstable haplotypes was treated by MG132.In summary,this study provides a certain experimental basis for a comprehensive understanding of the mechanism of APOBEC3 H regulating SVA retrotransposon.The results indicated that A3H_HapII can bind with SVA RNA and promote the formation of stress granules.It could be the mechanisms of A3H_HapII on SVA inhibition.Our study provides a theoretical basis on understanding the diseases caused by retrotransposons.