microRNAs决定哺乳动物的基因进化

"MicroRNAs  are  affecting  the  majority  of  protein-coding  genes,  either  at  a  functional  level  or  an  evolutionary  level,"  says  Andrew  Grimson,  a  post-doctoral  fellow  in  Bartel's  lab.

In  order  to  make  a  protein,  a  gene  codes  for  a  specific  molecule  called  messenger  RNA,  or  mRNA.  Each  mRNA  molecule  contains  a  blueprint  for  making  a  protein.  A  microRNA  can  bind  to  a  short  sequence  on  a  targeted  mRNA  and  suppress  protein  production.

In  a  paper  published  last  January  in  the  journal  Cell,  Bartel's  lab,  in  collaboration  with  Chris  Burge's  lab  at  MIT,  presented  evidence  that  one  third  of  human  genes  are  regulated  by  microRNAs.  In  this  new  study,  published  online  Nov.  24  in  Science,  the  researchers  demonstrate  that  microRNAs  affect  the  expression  or  evolution  of  the  majority  of  human  genes.

Nearly  all  genes,  the  authors  explain,  contain  short  sequences  that  match  portions  of  microRNAs.  Some  of  these  potential  microRNA  target  sites  are  evolutionarily  "conserved,"  meaning  that  they  show  up  in  the  same  spot  on  the  same  gene  across  species  as  disparate  as  the  mouse  and  the  chicken.  The  authors  of  last  January's  Cell  paper  showed  that  thousands  of  human  genes  contain  microRNA  sites  that  are  conserved  in  this  way.  To  the  extent  that  evolution  has  preserved  these  sites  more  than  would  be  expected  by  chance,  scientists  have  regarded  them  as  sites  that  microRNAs  target.

But  is  a  matching  sequence  all  that's  required  for  microRNA  targeting  and  gene  regulation,  and  do  nonconserved  sites  also  have  the  potential  to  disrupt  protein  production?

In  the  new  study,  scientists  in  the  Bartel  lab  designed  an  experiment  that  zeroed  in  on  these  nonconserved  targets.  Grimson  took  mRNAs  whose  target  sequences  were  not  conserved  and  exposed  them  to  microRNAs,  which  latched  on  without  a  problem.  The  experiment  proved  that  a  matching  sequence  is  generally  sufficient  to  disrupt  mRNA's  ability  to  make  protein.   (责任编辑：泉水)

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microRNAs决定哺乳动物的基因进化