r - 仅解析括号内的术语

Question

如何从我的数据框中解析出括号内的术语

regulation of transcription from RNA polymerase II promoter (GO:0006357)         
regulation of transcription, DNA-templated (GO:0006355)                          
positive regulation of transcription, DNA-templated (GO:0045893)                 
positive regulation of transcription from RNA polymerase II promoter (GO:0045944)
 

我的预期结果是以下不带括号的术语

GO:0006357 
GO:0006355
GO:0045893
GO:0045944

标签： r