Sulfotransferase that transfers sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the C-6 hydroxyl group of the GalNAc 4-sulfate residue of chondroitin sulfate A and forms chondroitin sulfate E containing GlcA-GalNAc(4,6-SO(4)) repeating units. It also transfers sulfate to a unique non-reducing terminal sequence, GalNAc(4SO4)-GlcA(2SO4)-GalNAc(6SO4), to yield a highly sulfated structure similar to the structure found in thrombomodulin chondroitin sulfate. May also act as a B-cell receptor involved in BCR ligation-mediated early activation that mediate regulatory signals key to B-cell development and/or regulation of B-cell-specific RAG expression; however such results are unclear in vivo. n 3'-phosphoadenylyl sulfate + dermatan 4'-sulfate = n adenosine 3',5'-bisphosphate + dermatan 4',6'-bissulfate + n H(+) n 3'-phosphoadenylyl sulfate + chondroitin 4'-sulfate = n adenosine 3',5'-bisphosphate + chondroitin 4',6'-bissulfate + n H(+) Inhibited by phenyl beta-GalNAc(4,6-SO(4)). Homodimer; disulfide-linked (Potential). The relevance of homodimerization is however unsure. May interact with phosphorylated proteins in resting B-cells, including HCK. A small fraction may also be present at the cell surface, where it acts as a B-cell receptor. Expressed in B-cell-enriched tissues but not in fetal or adult thymus. Expressed in fetal and adult spleen, lymph node, tonsil, bone marrow and peripheral leukocytes. Not expressed in T-cells. In pro-B, pre-B, and mature B-cell lines, it colocalizes with RAG1. Glycosylated. Belongs to the sulfotransferase 1 family.