I think you almost had it. Try:
TextFormatRemove (Filter ( Sequence_f; "ATCG" ))
TextFormatRemove ( Filter ( sequence_f ; "ATCG" ) )
Thank You for the help.
when I pase some thing in the field with lowercase letters result is blank. I change the ATCG to lowercase letters on the formula, then when I paste uppercase letters field is blank. Could you please help me to resolve this problem.
The Filter function is case sensative. Is it possible the text in field "Sequence_f" does not contain instances of these letters in uppercase? Try filtering on both upper AND lowercase, as in:
OR, you could convert all text in "Sequence_f" to uppercase, as in: