Sequence-specific and methylation-dependent and -independent binding of rice nuclear proteins to a rice tungro bacilliform virus vascular bundle expression element

Nuclear proteins from rice (Oryza sativa) were identified that bind specifi cally to a rice tungro bacilliform virus promoter region containing a vascu lar bundle expression element (VBE). One set of proteins of 29, 33, and 37 kDa, present in shoot and cell suspension extracts but hardly detectable in root extracts, bound to a site containing the sequence AGAAGGACCAGA within the VEE, which also contains two CpG and one CpNpG potential methylation m otifs, Binding by these proteins was determined to be cytosine methylation- independent. However, a novel protein present in all analyzed extracts boun d specifically to the methylated VEE. A region of at least 49 nucleotides o verlapping the VEE and complete cytosine methylation of the three Cp(Np)G m otifs was required for efficient binding of this methylated VBE-binding pro tein (MVBP).