def concat_RNAP_sites(df):
    """Concatenate all binding sites from DataFrame into list."""
    outsites = []
    for i, row in df.iterrows():
        q = row["sites"]
        q2 = q.split()
        q3 = [int(x) for x in q2]
        outsites = outsites + q3
    return list(set(outsites))