A recombinant polypeptide is described which comprises at least one PUF RNA-binding domain capable of specifically binding to a cytosine RNA base. The PUF RNA-binding domain of the polypeptide comprises at least one RNA base-binding motif of the general formula X1X2X3X4X5X6X7X8X9X10X11 wherein X1 is selected from the group including glutamine (Q), valine (V), methionine (M), proline (P), glutamic acid (E), and lysine (K); X2 is selected from the group including histidine (H), phenylalanine (F), tyrosine (Y), and asparagine (N); X3 is selected from the group including glycine (G) and alanine (A); X4 is selected from the group including glycine (G), alanine (A), serine (S), threonine (T) and cysteine (C); X5 is selected from the group including arginine (R), tyrosine (Y), histidine (H), and asparagine (N); X6 is selected from the group including phenylalanine (F), leucine (L), and valine (V); X7 is selected from the group including isoleucine (I), leucine (L), and valine (V); X8 is arginine (R); X9 is selected from the group including leucine (L), lysine (K), arginine (R), glutamine (Q), and histidine (H); X10 is selected from the group including lysine (K), phenylalanine (F), alanine (A), cysteine (C), isoleucine (I), valine (V), leucine (L), and methionine (M); and X11 is selected from the group including leucine (L), phenylalanine (F), isoleucine (I), and valine (V); and wherein the RNA base-binding motif is operably capable of specifically binding to a cytosine RNA base.